What I did as part of my dual battery install was buy three of these Bussman automotive fuse blocks ($8 each):
One is mounted under the hood, one is mounted in the glovebox next to the stock fuses, and one is mounted in the rear Add-A-Trunk. I connected them with a 4-guage wire to the battery switches, and run the power to the 4-guage wire through a single 140-amp main ANL fuse and fuse holder:
...everything else is just wires with battery lugs crimped on the ends. My total investment was less than $50 on these three fuse blocks.
To add a circuit, all you do is select a blade fuse of the correct size for the load, and plug it in one of the fuse block slots. The fuse energizes the adjacent spade lug. I do not have to run more than about 4' of power wire to reach any part of the Jeep from one of these fuse blocks, very convenient. The three 8-circuit fuse blocks allow me to add up to 24 auxilliary circuits.