what the........

I have a straight razor design black latigo strop and for some its not flat but concave.....is there some way to get it flat?

try rolling with a bottle or rolling pin

If some part of a strop is concave, then try cupping the edges of the strop in that area with your hand and purposely make it convex; then, with an open palm, rub your flat palm over the taught strop. purposely overcompensating the opposite way then flattening it out with your hand usually solves the problem.

Chris L