Building a large hill

I am in the process of planning to build on a large hill in Dorest, Ontario. I will use conventional piers at the back but as the property sliopes toward the road and eventually slopes to a lake, I am planning to use approximately 4/5 foot pressure treated posts for the front elevation

My question is: If I cannot get four feet down to beat frost before hitting rock (its the Lake of Bays) how can I stay level and keep the lumber steady on the rock assuming it's not going to be flat.

Some have suggested grinding a level surface but I think it may compromise the rock. Any ideas?

Thanks for your input,

Rob