I think I saw ger21's video you mentioned but don't recall much about it. But my recollection is that he uses a Z touch plate to zero to the table or spoiler board surface at a given location on the table. My suggestion was that this might be expanded to also have an XY touch-plate in this same are, although where the "touch" would occur at XY=0. I've seen it done both ways, auto zero XY and Z with a 90deg aluminum angle standing upright near 0,0 and a flat plate on the work surface to auto zero Z, or with the XY and Z plate moveable to anywhere your work 0,0,0 is to be. Although I do not use a stationary location to zero my XY or Z.
I use the Mach3 "Ref All Home" to zero to the table XYZ limit-switch limits (this homes the Z-axis to top of travel). And use the moveable XY angle touch-plate, flip it on a side if I'm also using it to zero Z or a separate, flat Z touch-plate for Z. I've got a number of posts on this forum on this I put up years ago.
Everything depends on everything else