Tape the tiles and plaster or mdf strip if you happened to have moisture resistant mdf in the right quantity available. then paint it to match the ceiling.
Yeah I think tape the tiles, a rubber float and ready mix plaster.
Tempted by a small guide strip of dowel. Width of tile, that I can then remove and fill after too.
The tiles have a crackle glaze so when cut pieces fall out. Luckily in the rest of the bathroom this is generally out of eye line.
Tape the tiles and plaster or mdf strip if you happened to have moisture resistant mdf in the right quantity available. then paint it to match the ceiling.