Susan... the foam comes 4' x 8 ' to make it thicer just stack them.. HA HA I'll show you sculpted foam at the end...
so I have the planters.. or anything... I use a synthetic stucco to cover it with.. Parex... here's a few hundred available finishes...http://www.lahabrastucco.com/colorcharts.shtml
on items that don't requre a bunch of heavy ddurability I just use the stucco.. but you can imbed a fbergalass cloth in it [ like the mesh sheetrock tape only in bigger rolls.. but for small projects you can use that ] to give it durability...
did you ever wonder how in vegas they made vennice.. New York... Egypt... it's all stuccoed foam.. you can get any look...