Hi Mary Stella,
those shallow planters actually work just fine for small and middle sized semps. Best if you already have a drainage hole -otherwise you have to cut it on your own. The planter in the foto (taken last summer) has about 14" in diameter at a height of about 1.5". Obviously my plants do not get as big as they could with lots of space and nutrients, but they look healthy, grow and just start multiplying after winter dormancy..
