This is roughly what I think you need.....just bring the back part of the template around in a nice even curve at the crown point sitting it down so that it joins the `good`/strong growing hair which you will be keeping..use a hand-held mirror while sitting in front of a fixed/dressing table mirror so you can see what you are doing/marking at the back. Apologies for my unsteady hand while marking this... Paul.
p.s. ---- if you have any old pics to hand --especially side-views --of when you had all your own hair, enclose them with your order as they will really help them to replicate your swept-back style and even a current pic of your remaining side/back hair will ensure a good density and `wave/ curl` match.