I have a somewhat unique patio project coming up soon and I was looking for a little insight on how you guys might approach the base prep. The patio will be using Techo econo slabs, 12"x24" in a herringbone pattern. The house is new construction, built on a slab with 4' frost walls. It sits atop a fairly good size slope. The driveway to the house is probably a 30 to 35 degree slope. The sight was a lightly wooded area with trees all under 2" diameter. Site work included light grading of the house site and driveway construction, then approximately 2' of sand used to create the finished grade. Then entire hill side is sand underneath whatever top layer the trees are growing in. So essentially, a soil profile of the site is 24" of sand, 6" to 8" forest soil, then sand.... Also of note, the builders installed 2" foam board, 6" deep and extending 4' from the foundation, laying flat. We get cold winters in these parts, with much snow cover. The entire area is obviously very well drained. what would you guys use for a base? Dig down the two feet to the original soil line and build up a gravel base from there? Dig further? Or just the normal 6" to 8" base with geofabric? Also, how would you deal with the foamboard insulation?