Here is a simple way to make a fly box for your nymphs and midges.
The items needed to make one.
1/4 inch white closed cell foam (big box craft shop .99 cents)
Combination square/steel ruler (for making nice straight cuts)
Xacto/utility knife
Crazy glue (your favorite brand)
Pencil (for marking the foam)
Box (altiod tin or plastic equivalent. I used a gift card tin box from cabelas $1.99)
Pinking shears. Yes pinking shears!
Measure and layout how many strips of foam will go in your fly box. This is where you use the pinking shears to cut the foam on one side and the utility knife on the other side
After all of the strips have been cut to the length and width required to fit inside the box, use the utility knife to cut the slits in the foam to hold the fly.
After all of the slitting is done, all thats left to do is to glue in each strip to the inside of the box. Space the strips accordingly inside the box.
Once the glue has set, add the flies into the slits in the foam.
Repeat the entire construction process if you want to add the foam strips to the inside of the cover.