There are a lot of assemblers, but I've used MASM. It ships with visual studio. I think you can find the actual binary by searching for ml.exe or ml64.exe. Then

There are a lot of assemblers, but I've used MASM. It ships with visual studio. I think you can find the actual binary by searching for ml.exe or ml64.exe. Then you just write some MASM code and assemble it. It's less well documented but entirely possible.