i use screened bottom boards, but they are closed about 8 months out of the year. they are another thing that you can skip if your budget is an issue. some of us really like them, but some, like JP have switched back.
if you go the cinder block route, make sure you do as lenape suggests and have a good base. i don't remember who it was, but someone on here found their stand shifted in the mud and dumped their hives. you don't want that!
KISS! keep that in mind and you will be fine.