In 9.5 SP1 you should be able to use the Create Partition action that does the whole thing (create, format, mount, etc.) all in one. Your template for UEFI should look like this:
Create Partition:
GPT box selected
Type = EFI Boot Partition
Size = 350 MB (generally)
Format, yes. FAT32
Mount, yes. Drive letter = S (This is what MS uses in their example scripts, so we'll do it to stay consistent)
Create Partition:
GPT box selected
Type = MSR
Size = 350 MB
Format, no
Mount, no
Create Partition
GPT box selected
Type = Primary
Size = blank (the rest of the drive)
Format, yes. NTFS
Mount, yes. Driver letter = C
Then deploy your image to drive C.
After you deploy your image and sometime before CTOS you need to run:
bcdboot.exe C:\Windows /s S:
That will create the BCD files and everything needed for the boot partition. You do not need to capture/deploy the boot partition separately, if you were doing that.
Let me know what questions you've got and whether or not this works.
Thanks!