They are easy to access Andy, the difficulty is if you mount something behind that trim panel to use the space up, then it's hard to access, really needs the load barrier and drawer top removed to get the panel off and get at whatever is behind.
The covers have a tab at the bottom that hooks over the bottom edge of the hole, like the OEM cubby hole covers do, and some velcro up the sides holds them in place. The bigger cubby is more than big enough for a couple of 1ltr bottles of oil and some rags, which is what I'll probably keep in there.