We found our Thetford Porta Potti 145
way too low. To make it easier to use I added a 120mm platform
to match the height of our toilet at home. No doubt there are a
number of ways to do the same job.
Using 12mm plywood I cut
two lengths the width of the portable toilets diagonal length
adding stoppers on the end. Two slots were cut to allow them to
join together & pull apart to pack flat in the camper trailer.
I used an old tent peg & a bit of steel angle to make a brace to
lock the two parts of the platform in place.