or just buy concrete blocks at ~1.25$ each and easily stackable since they are totally ‘squared away’ facilitating building garden beds like lego. May not even need a mixer since you simply just apply masonry mix at the rims of the hollow blocks, so won’t need large amounts of concrete. Posted our process of building concrete garden beds here. Totally agree though that it is a lot of labor, but way more productive than having to go the gym. Pumping iron only builds muscles.
Handling, transporting, and manually mixing cement slurries and concrete not only just build muscles, but also builds long-lasting stuff 