I had seen some of the other threads on distribution blocks and decided to add one to my bike. I wasn't too excited about the un-fused blocks. I did like the Blue Sea fuse box installs I had seen, but I did not like that they were tucked in the tail in a spot that is inaccessible unless the plastics are removed. So, shopping I went...
I found this fuse block on eBay -- it comes with pigtails for 6 fused circuits and 2 hot input leads, so you could run 2 relays or have 3 switched terminals and 3 unswitched. I chose to go with one relay and have all six terminals switched. Note: I added those connectors after buying it -- it comes with just the wires. Here is a link to the sellers store.
My neighbor is a car stereo installer, so he has about a 100 automotive relays lying around, and I found this one in his stuff. Uniquely and conveniently, it has 2 power-out leads, which works perfectly with my fuse block. You should be able to find a similar set-up, although most only have one wire for the power out, but you can just crimp or solder the one wire to the two wires on the fuse block and it will work the same.
After a little tinkering, I decided to mount the fuse block on one side of the rear fender and the relay on the other side -- You will see how nicely this works out in just a bit. I used speed nuts on both sides with stainless screws. Here is a picture of the speed nuts on the fuse block side:
The fuse block does not have common (negative) terminals, but rather than use a plastic strip, I got a stainless bolt and put it in the forward compartment under the seat -- now I can just put a ring terminal on the negative wire from the accesory to be installed and add it to the post (ignore that in-line fuse wire -- it doesn't belong there):
And here is a picture of it all installed. I should probably label this picture so you can see the different parts, but there is a fused connector from the battery positive to the power input on the relay and a jumper connected from the negative battery terminal to the negative post. The relay switch is connected to the license plate light (you can see it at the very rear -- it is a pink/red tee-tap). The negative from the relay goes back to the negative post and the two power wires are connected to the two inputs on the fuse block. Any added accessory would connect to one of the fuse fused terminal wires and the negative post. Note: I did have to sand off the upper front corner of the fuse block to clearance the frame -- it took about 5 minutes of easy sanding with a small hand block -- you could get around this by lowering the attachment point, either by using a regular nut or not clipping the speed nut over the plastic or notching the plastic, but I wanted the stability of the nut over the plastic and the fuse block sanded so easily that it seemed like a fine solution.
What I like about the way this turned out is that it looks OEM, leaves the undertail area mostly free for storage, and all the parts are fully accessible without removing the tail plastics.
As a side note, if I wanted to save myself a lot of trouble, I did come across this clever little 3-way fuse block that is basically plug and play, and would probably be plenty good enough for most needs. Linky.
I found this fuse block on eBay -- it comes with pigtails for 6 fused circuits and 2 hot input leads, so you could run 2 relays or have 3 switched terminals and 3 unswitched. I chose to go with one relay and have all six terminals switched. Note: I added those connectors after buying it -- it comes with just the wires. Here is a link to the sellers store.

My neighbor is a car stereo installer, so he has about a 100 automotive relays lying around, and I found this one in his stuff. Uniquely and conveniently, it has 2 power-out leads, which works perfectly with my fuse block. You should be able to find a similar set-up, although most only have one wire for the power out, but you can just crimp or solder the one wire to the two wires on the fuse block and it will work the same.

After a little tinkering, I decided to mount the fuse block on one side of the rear fender and the relay on the other side -- You will see how nicely this works out in just a bit. I used speed nuts on both sides with stainless screws. Here is a picture of the speed nuts on the fuse block side:

The fuse block does not have common (negative) terminals, but rather than use a plastic strip, I got a stainless bolt and put it in the forward compartment under the seat -- now I can just put a ring terminal on the negative wire from the accesory to be installed and add it to the post (ignore that in-line fuse wire -- it doesn't belong there):

And here is a picture of it all installed. I should probably label this picture so you can see the different parts, but there is a fused connector from the battery positive to the power input on the relay and a jumper connected from the negative battery terminal to the negative post. The relay switch is connected to the license plate light (you can see it at the very rear -- it is a pink/red tee-tap). The negative from the relay goes back to the negative post and the two power wires are connected to the two inputs on the fuse block. Any added accessory would connect to one of the fuse fused terminal wires and the negative post. Note: I did have to sand off the upper front corner of the fuse block to clearance the frame -- it took about 5 minutes of easy sanding with a small hand block -- you could get around this by lowering the attachment point, either by using a regular nut or not clipping the speed nut over the plastic or notching the plastic, but I wanted the stability of the nut over the plastic and the fuse block sanded so easily that it seemed like a fine solution.

What I like about the way this turned out is that it looks OEM, leaves the undertail area mostly free for storage, and all the parts are fully accessible without removing the tail plastics.
As a side note, if I wanted to save myself a lot of trouble, I did come across this clever little 3-way fuse block that is basically plug and play, and would probably be plenty good enough for most needs. Linky.