Built and sold quite a few--You really dont need a plan. If you look at your picture it will give you a good idea about size of every thing starting with a 12 x 24 base. The side and back boards 2 1/2 to 3 inch wide. The main board can be purchased in a hardware store ready cut--a bread board. Dont buy the one sold for cutting meat. Their oily. Another thing to concider--do you use a C clamp vise? I dont like the vise as shown in your picture -- I feel you would be tying too high. Go to GOOGLE and type in "Fly Tying Bench" for more ideas. Also
http://globalflyfisher.com/tiebetter/tying_bench