I am remodeling a bathroom. It an an existing fiberglass shower basin. It is not cracked put it is discolored. I don't want to make a new basin. I was wanting to know how to use the existing basin and tile it with 1" travertine tiles. On the walls I am putting 12" travertine tiles.

The fiberglass will likely flex and the tiles will pop off...

I'm unaware of a good way to adhere tiles to a fiberglas pan.

Some hints are in here: https://www.askmehelpdesk.com/interior-home-improvement/shower-stall-tile-floor-70907.html