The speakers standoff the inner door skin by about 40mm, so you need 2 x 18mm MDF rings glued together with a bigger 6mm ring to secure to the door skin. You can use the stock speaker as a template. Or an easier but more extreme route is to cut the original speaker out of its plastic adapter and mount the new units to the old one.
What you will need are some spare pop fasteners as the ones on the door card are designed to snap when you take it off. They are not expensive and your dealer should have them in stock. I'd buy about 8 of them just to be safe