Haymish Pupkin wrote:

I need to seal a shower tray but the tray is 0.5"-1" away from the wall at
the back (the wall facing you as you walk into the cubicle). I have filled
the hole with plumbers mate putty and now I'm not sure what to do next.

I could fit a long thin strip of WBP ply over the gap along the length of
the back wall so that it over hangs across the tray by half an inch or so,
then I could seal / stick it to the walls / the shower tray with no more
nails or silicone or something where the ply meets the tray, then tile over
the ply and seal with grout. Does that make sense? I assume nothing will
stick to the putty I have used. Would someone walk me through the process of
what I should do / not do to seal a gap like this?

What's the overal status here - is this an existing tiled shower in
which you're trying to repair a hole, or a completely new installation?

IMHO flat areas within showers are to be avoided like the plague; yes
they can be sealed but they are inevitably the first place to leak.
*If* it's a new install, I'd be looking at battening out the wall and
applying aquapanel board to that, then tiling the aquapanel so the tiles
can be sealed directly to the shower tray, thereby eliminating the flat
strip.

David