With outdoor pots, big and small, I like to nest one inside another, especially if the pot itself gets direct sunshine. That allows the outer pot to keep the inner one in the shade, hence cooler. And I think coolness is important - as soil in a sunned pot can get hot, and if it has been watered, you can end up cooking the roots (which like to gather next to the side of the pot). Using the pot-in-pot technique also allows you to plant in a cheap pot, and use an expensive decorative pot outside - without fear that in future you might risk breaking the expensive one at repotting time (especially if the pot is not wedge-shaped). If the inner pot is pottery, it can still breathe.