Here's a "trout only " answer from a person who fishes mostly trout.
Dries on the left; by the season (little black stones, blue quills, hendricksons/red quills, quill gordons, march browns, sulfurs, green drakes, slate drakes, yellow sallies, caddis, attractors (humpies, wulffs, stims). Soft hackles at the bottom on the left side (partridge and almost anything, Leisenring/Hiddy patterns).
Nymphs on the right (pheasant tails, hare's ears, princes, chironomids, worm patterns). Small selection of terrestrials (ants, chernobyl ants, hoppers, crickets), buggers/streamers at the bottom on the right side.
That's box #1!
It's a good sized box!