If your billets are board billets, you need to do a Z splice then glue them together.
The boo, you need to flatten the belly side, then draw your bows pattern/shape on it and cut it out.
But first, Position the boo nodes so they lay an equal distance apart on each limb, in other words they look even on the bow.
I flatten my boo with a drum sander.
Then taper the boo from 1/8th thick at riser to 1/16th thick at tips.