I think there are some manufactured fixed "full frame" carriers. But, most people mod their own buy using a file.

The previous owner of my enlarger filed the carriers, but the opening doesn't give an even boarder around the neg area for the negs from my most-used camera, hence I never bother with trying to include the rebate area.

For the LPL you can buy a carrier that has an adjustable mask, which might be better than the filing method.