There's a number of different things you can do to make a coffee low-acid. We'll combine all the tips in this post - using a low acid origin, lowest acid roast, and lowest acid brewing method.
Combine 36g (1.2 oz) dark roasted brazilian coffee with 360g (12 oz) room temperature water in a french press or other container
Store in fridge for 12-24 hours
Remove coffee grounds from water either by straining
Serve within 24 hours