An oat milk factory would be importing bulk quantities of oats and flavoring agents like cinnamon, vanilla, maple syrup (which maybe be processed by expensive factories). I would just be going out and buying these things separately and tossing it in a blender with random measurements until it tasted the way I like. No factory required for me. T'would be even better to grow the ingredients myself, but I do not think a vanilla bean vine tolerates low temperatures. Same with cinnamon. Oats would be easiest to grow, and I'd imagine there would be some threshing and winnowing involved (manual labor opportunity). Might as well let the combines and tractors harvest millions of bushels and I just spend my nations currency to acquire a 50 lb bag every few months (storage in cool/dry place).

I suppose purchasing a colorful carton adorned by lots of writing in the "Vegan Isle" of a grocery store could be an easier way because the aforementioned steps may be far too time consuming for most people who want everything pre-prepared for them by a favorite brand and stored in plastic/cardboard/glass individual packaging.

Meat is a different story, because coordinating the grazing routines, herding (some canine breeds are helpful for this), winter hay feeding stockpile, veterinary treatments, calf birthing, nutrition feed deficiency compensation, slaughter (bolt-gun to forehead is most humane), blood drain (good composting material), and butchering into desired cuts would be consuming much more time than available in a highly specialized life.