I have built a box and wonder if I should put in gravel before the soil?
Certified GKH Gardening Expert
I would, definitely, add some drainage. There are a lot of things you can use for this. My favorites are Hydroton (baked clay pellets) and something called growstone (Expanded recycled silica from glass) These are the best ways to get good drainage, but gravel will do if you don't have access to these.