Question about Samsung EP-PA510 Wireless Charger Pad

That should work in principle. Unfortunately, I can't tell you whether the leather case might not be too thick. You can only really try it out. There is no official support for Qi wireless for the iPhone 6s Plus that explicitly says: It works with the leather case! It works with Qi adapter from Maxfield! It works with EP-PA510 Wireless Charger Pad! You don't just have one unknown here, but three. The case is probably the least of the problems.

Adapter is purchased from the Maxfield brand.