This is what my dad told me he did years ago in his first house. Said he built a wall and lobbed every single bit of rubbish he had into it. Everything from rubble to an old motorbike. Topped it off with soil and had a nice tiered garden once he was done.

I don’t want to be chucking any old shite in though as I’d like to at least consider the environmental impact if there was one. Hence why I won’t be burying plasterboard