ok here we go
step 1 build the desired shape out of wood, strach a layer of old tshirt, felt, flanel whatever you have staple and glue it up. when this is done it should look like the final shape just not hard yet
step 2 mix up some resin then coat the fabric in it, at the same time have a box of 6 inch ripped piece of mat and apply them until you have 3-4 layers.
step 3 once dry scuff it up the apply filler and sand then prime/shadow coat it, refill it, prime, glaze, sand then primer and sealer, paint
wait a week or two and i will build a box and take pics for you