Help with making a macosx boot drive

As above, i am trying to use OpenCore to make bootable usb for mac os. Specifically im trying to make a mac el capitan installer for a imac from 2007.

I am trying to follow the instructions on the guide, but I am kinda lost. Especially around the part where it says cloning the recovery dmg to the Smaller partition.

How would I do this? Or achieve the same thing with the larger partition?

Author: @squidoeye23