kink, piss@kitten given I've made a raised bed in the garden im pretty sure this is in the realms of possible for me to make myself, but it would be impossible to hide from my house mate. And probably fill our wheelie bin with how much litter it would take
kink, piss@kitten humm ... damn it kitten you've got me thinking.
One of those collapsible rectangle frames with hinges in the four corners and some bracing brackets to keep the corners square. So you've got solid sides but they can be collapsed when you aren't using it or transporting it to a play space.
Then a thick plastic sheet or tarpaulin layed over the top with the litter poured in. With enough hanging out the sides you could pick up the sheet and dump the entire lot in the bin when its time to clean up.