You need a drop ear secured to some blocking in the wall with 1/2" copper or PEX supplying it. Depth of drop ear shouldn't be too critical. Just need to match up a nipple when the wall is up and tile or whatever the backsplash is is done. Then you just find the right length nipple for your pot filler connection to screw on to flush with the tile. Leave an 8" nipple capped in the drop ear for the time being while the wall is being completed for work to be done around it.