Assuming you have a surface for the shoe…
You could draw a curves for the outline of the strap. Then use those curves to split or TRIM a copy of the shoe surface. Then use OFFSETSRF to get the thickness.
Assuming you have a surface for the shoe…
You could draw a curves for the outline of the strap. Then use those curves to split or TRIM a copy of the shoe surface. Then use OFFSETSRF to get the thickness.