New to bow making.

[Bowjunkie]

For me it depends on what I'm backing the bow WITH. If I'm backing with sinew or rawhide, I partially tiller it. At least partially tillering a sinew backed bow allows you to pull the bow limbs into reflex before the sinew is applied, or better let the sinew to pull the bow into reflex as it dries. I have sinewed backed fully-tillered bows, and after the sinew dried, they needed very little tiller adjustment.

Rawhide, or other backings meant to protect the back can generally be applied any time after the bow is shaped to an accurate front profile. I usually do it after floor/early tillering.

Decorative stuff like snakeskin you can do after it's done being tillered.

[macbow]

My suggestion is to forget the sinew especially for now.
Doing,a sinew backing is,messy, time consuming, and ment for short bows. So for a fledgling bowyer sinew is too much too soon. Sinew adds strong tension and would be too much for a lot of woods.works well with Osage and Hickory.

I had the same questions on backing,when starting out.
I've,settled on using bamboo and sometimes hickory as backing. Gluing in R/D.
On your white oak board if there are run outs in the grain that could splinter then a,simple backing like paper or cloth may help.
Go through with making the bow. Tillering etc.
Many first bows are best thought of as learning tools. Most don't make it long. Then add the backing before doing finish work.