My recommendation is to keep reading and start in on a block of wood--trial and error is a sure bet, if your handy and I figure you are, to find peace and build yourself a darn good call in the fun process. I think you would have better success by working with a solid block of wood rather than a glue-up. I think it is more challenging and to me challenge and adversity always brings out the best. I don't know of any instructions and doubtful many of the masters are about to give any trade secrets, but if you go to www.customcalls.com
, look up under Turkey box and paddle calls and see the very first thread under important topics "How I make a box call" posted by Frozen Crow it is a great tutorial on how to make a box call. I don't recall the makers name, but he did a fine job showing and explaining how HE does it. There are variations of course and by your description I am willing to bet you will adapt your own approach and style and do just fine--enjoy!