I found this
study which demonstrated oxalates in spinach can be bound up by calcium:
Calcium is somewhat "protective" (I don't like using that word in this context) against absorption of
soluble oxalate if there is not intestinal permeability, because the calcium binds with oxalate to produce insoluble calcium oxalate which should not be absorbed (in a healthy gut). However, calcium oxalate is still irritant to mucosal tissue in the gut. It would also need to be taken at exactly the same time as the oxalate-containing food, because soluble oxalate can be absorbed right through the stomach and the upper small intestine.
People say that spinach contains calcium, but this is a misunderstanding. None of the calcium is bioavailable because it is bound up with oxalate, and it has a net-negative effect on calcium homeostasis because there is so much oxalate that it depletes the body of calcium.
Feeding animals spinach as the only source of dietary calcium source will kill them in a short period of time (90 days).
TBH, spinach is by far the worst vegetable that I know of, and under no circumstance should someone juice the stuff. Funnily enough I made a video specifically on this (below). There are numerous case studies showing acute kidney failure from juicing spinach. A juice can contain upwards of 1 gram in just 200ml. This is enough to cause kidney failure.
Honestly, I wouldn't rely on calcium as a means of protecting one from extremely high oxalate foods, unless on occasion. Like, if your gonna eat something you know is extremely high, then calcium can be taken at the same time to somewhat mitigate the effects. But almond milk as a staple? Its not worth it IMO. There are other much safer alternatives like coconut milk.
I used to binge on almond milk, spinach, and 100% dark chocolate, and it thoroughly screwed me up and I am still dealing with some issues from that.