Yuo didn't say how wide your bow is going to be.
I make my osage bows 1 1/4" or 1 3/8" wide. I use the same method on hickory bow blanks that are wider.
I make a 1/2" mark at the end of the fade and and drop the measurement 1/16" every 6" until I get to 1/4". I hold the 1/4" measurement to the tip of the bow. I start removing wood to my line but leave the belly rounded, I never go lower than a 1/2" thickness at the tip even though I have a 1/4" mark on the side. I drop the width to as low as 3/8" at the tip but the limb tip is 1/2" thick.
I tiller the rounded belly and reduce the oval shape to almost flat on my finished bow as I reduce poundage, the last 6" of the limb will remain somewhat rounded on the belly.
Others may make a wider, flatter limb bow profile, in which case the starting measurement will be less.