Good terra cotta pots can be expensive, because terra cotta pots that won’t crack are more expensive to create and import. Clay liners for chimney flues, however, are much less expensive than terra cotta pots.
These clay liners are constructed with hard-fired clay sectionals that can last for many decades, in a chimney. If they work that long inside a chimney, it seems like they might work well as bottomless container gardens. (Terra cotta chimney liners are often available at masonry yards.)
As a less-expensive alternative to making a mortared wall, wouldn’t it be fun to set these into the ground a few inches, side by side using different heights and sizes, and plant them all up like window boxes, or put them together in a group for an herb garden next to the kitchen door, or even use them to create a spiral herb garden. I’ll have to put this idea on my To Do list.