This shows how to build a working DLL in 64 bit MASM. The example shows manually how to set the stack space and load the registers into the first 4 arguments of a high level procedure. It also has a low level procedure that does not use the stack at all which has lower overhead than a stack frame based proc.
The Old New Thing here (https://blogs.msdn.microsoft.com/oldnewthing/20110302-00/?p=11333)
Thanks Tim, it tells me that doing it manually is a lot safer. :P