I'm planning on tiling a kitchen splashback (first time tiling project). Unfortunately due to curvature of the wall, there is a gap between the worktop and the wall. This varies in thickness between about 2mm and 9mm.
The tiles I'll be using are 6mm thick metro tiles (flat, no bevel), and I'm planning to use a 6mm square notched trowel – which by my research will mean the tiles will end up 3mm away from the wall.
I feel that there is a good chance that the tiles will slip down into the gap behind the worktop. My question is therefore: How should I stop the tiles falling down into the gap, and instead keep a level first row?
So far I have considered:
Plugging the gap with a strip of wood. Seems ideal, but unfortunately I don't have a suitable piece of wood nor the tools to craft one, and it is difficult to get hold of this sort of thing at the moment!
Filling the gap with caulk/grout/filler. This would be easy enough, but could I get a level enough surface to start the tiling from?
Tiling off a metal rule. I can't re-find it now, but I read somewhere that you can lay the first set of tiles on top of a metal ruler – presumably laid flat on the worktop? Could this help to form a temporary 'bridge' over the gap?