Well, I just finished putting it together, and found out the last 5 pics vanished!
I'll put together a drawing of it later and post it.
Here are the first 3 pics. After this I cut the top part of the bag off, cut a hole in some burlap and fit it over the bag. Then I fit some cloth over the end of the fill pipe and buried that end in the perlite through another hole in the burlap.
Then I buried it all in the soil.
The overflow hole is 5cm up from the bottom of the tote, and the perlite is 7cm deep (no autocorrect, that should not read "derp").
What else am I missing?
Turns out 10 litres of perlite wasn't enough, so I ended up using 15.
In the second pic you can see the divot I made in the perlite to drill the overflow hole.
There was a plant growing out a hole in a bag of soil too.
I put some burlap and bricks on top of the soil to keep the squirrels out.