The Crooked River is outstanding fishing on nymphs and dries. The afternoon mayfly hatch is a mix of #16 PMD’s and #18-20 BWO’s. Noon to 4 is the best bet for timing the best hatches of the day. 
Nymphing is red hot, either the Euro method or try a NZ Wool Indicator or the (newish) tiny Oros indicator with a single nymph for great strike detection. Micro Mayflies to imitate PMD’s are brown #16, and either Olive or Black #18-20 to show the fish a BWO nymph imitation. Micro May’s are an old Northern Cal fly, invented by Mike Mercer and have proven themselves in every river mayflies and trout coexist. If you don’t have these little tungsten nuggets in your nymph arsenal, you need to add them. 
Do you tie flies? I love to tie a little simple mayfly nymph pattern that have proven itself on the Crooked a lot. Here is is: #16-18 Short Shank or 1XL Nymph Hook. 2.8 or 3.2mm Gunmetal Tungsten Bead. Coq de Leon tail. UV Ice Dub Brown (in the package it appears purple to our eyes). Rib body with Silver Fine Wire and build up the thorax just a touch with the same Dubbing as the body. I usually tie it with black 6/0 thread, but have been playing with Red 6/0 as it adds a subtle Hot Spot. I learned about the Red Hot Spot from a Garret Lesko podcast and I like the hot spot being a little less “hot” than fluorescent orange on some of my flies. Try this fly. It works on all the rivers, but is one I go to on the Crooked more and more.