Seal the back and ends and wait for it to dry. Hackberry bends well with steam if you want some recurve on the tips. Toast the belly to keep set to a minimum.
I built a few in typical flatbow style, roughed out at 2" wide limbs, finished limbs were 1 7/8" wide. My layout would be 4" handle, 3" fades, 12" to 14" parallel (depending on desired bow length)at 2" wide then taper to tip. Probably 66" to 68" long NTN. See TBB volume one, page 135 for flatbow style layout.