[HayZee518]

ok, then I'd advise you dig down and put in a layer of 2 inch foam beneath the slab. around the edges pour a footing below the frost line to keep the foundation from shifting due to frost heaves. put foundation bolts in the pour so you can bolt the plate to the top of the concrete when it's cured. use a layer of poly foam between the plate and the concrete. use pressure treated for a plate and I'd go with 2X6 not 2X4. stud up your wall(s) in one piece then lift it into place and fasten to your existing wall after it's completely plumb with 16p spikes. do the same on the other wall. after it's square ( measure from corner to corner with a tape or string) nail together.