I'm not smart enough to build my own serious FAK so I just bought an AMK Comprehensive Kit. I suppose it's a good kit, but the FAK I've used more often is a 4"x3.5"x1" pocket kit labeled "Johnson&Johnson" that I modified with a few band-aids, one 2"x2" gauze pad, two 2"x2.25" adhesives pads, "Wash'n Dri" towlette, cleaning wipes, alcohol swabs, Povidone-Iodine pads and a small tube of neosporin.

Edit: The original J&J kit can be found at:
Johnson&Johnson First Aid To Go Mini Kit

Normally that FAK is kept in a vest I wear when walking dogs and doing other things in the great Interstitial Wilderness (I'm not Bill) but it fits easily into thigh side pockets too. That said, the kit is small and really just designed to clean superficial wounds and cover relatively small boo boos.

For anything outside the scope of "superficial", the AMK Comprehensive Kit is in the truck. There are two pair of nitrile gloves in the vest, but not part of the pocket kit; additional gloves are in the truck's kit.

At home I have another nice convenient boo boo kit and a larger kit made up of bulk refills for the other kits which includes larger dressings not in any of the kits, bottled Iodine, hydrogen peroxide et al.

FWIW