Summary

Designed quickly as a practice cab with a decent 1x12 in it (instead of the usual 8 or 10 inch speaker).
Suitable though for band practice or for gigging.
Angled baffle so you can hear yourself clearly and don't have to turn up too loud.
With a 1x12, especially with an open back, there's no difference in sound dispersion whether you go tall or wide for volume, so this one goes tall. That way the cabinet is easier to move around the house and has a smaller footprint. It doesn't bash doorways :)
It's also nicer than tilting a regular cabinet because the speaker is higher up, and it has a flat top, where you can put your modeller etc and it won't slide off. Also there's no handle on the top so the surface is clear.

Around 30 litres of spatial volume - you can put a back on it, but I have left mine with an open back as that's the sound I like (eg. Fender open back combo style).
I used 18mm plywood for mine, but actually the plans are using 20mm just to save time. It worked out fine for me when i made it, no issues with getting everything to line up.

I powered this with a Fosi Audio v3 power amp - which is a Class D hifi amp with a TPA3225 chip and the 32v adapter gives a huge amount of clean headroom without risking blowing the speaker (I used a Vintage 30). I will probably house the amp on the underside of the cab somehow, and have a single input to hook it up.

This object was made in Tinkercad. Edit it online https://www.tinkercad.com/things/luEXhcQtIU2