If you look in the "how-tos and build-a-longs" section, there's probably something in there to get you started. Ten pages of good accumulated knowledge. I know Gordon has a build-a-long somewhere in there with a small hazelnut sapling. Keenan did one from a juniper limb, probably more in there if you look around. I've made a bow or two from 2" saplings, that's about as small as you can go and still get a decent-weight bow. 2 1/2"-3" would be better, but it can be done with what you have. I would take the bark off and take some wood off of the worst side so that it doesn't have radial splits and cracks as it dries-whole, round pices of wood usually check badly. Do you know what type of ash it is?