For me, assuming the boards are suitable and been fixed correctly. prime boards, connect underfloor heating alarm to feed to detect any damage whilst working, lay underfloor heating (if matting, a good tip is to use some spray on floor adhesive to help stick matting down as it can bubble up and rise to surface sometimes when used with SLC) take picture of position of underfloor heating, fill any holes in floor with something like expanding foam or whatever suites, then a suitable SLC fibre enhanced, leave to dry, prime again, tile leaving a small (between 3-5mm) gap around edge for expansion and movement, grout, dry, Silicon colour match around edge and jobs a good'un! 😉