Although the majority of my work has been with osage I have made a couple of board bows that were really good shooters. After digging through both lowes and home depots piles of boards I came up with two good boards and a lot of bewildered looks from employees... The better of the two turned into an unbacked 72 inch pyramid flat bow. I took the full 2 inches wide at the handle and down to 3/8 inch at the tips, it ended up just shy of 50 pounds at 27" and took around 1 inch of set during tillering, it was a fun bow.
Do everything you can to keep from going to the dark side... I'd avoid fiberglass. You can make a great bow without it, and learn more on the way in my opinion.
Good luck!