How do I make sure a linear shower drain sits completely flush with the floor tile so no one trips on it?

Nine times out of ten, people set the drain channel flush with the sloped base before factoring in thinset mortar and tile thickness, leaving a toe-stubbing lip. Dry-fit your tile next to the drain using your exact thinset notch depth to set the height, aiming for the grate to sit roughly a sixteenth of an inch below the tile for proper drainage. If you haven't tied the drain into the trap assembly or sealed the waterproofing membrane yet, call a licensed plumber—getting that connection wrong will rot out your subfloor.