Kinda hard to describe this. On my island / bar the main cabinets have a granite countertop and sink. The cabinets are attached to 2x3" wood strips that go around the inside of the cabinet and toe kick area, and the strips are screwed to the floor. The way to do this is to trace the cabinet on the floor and then screw down the nailer blocks at least 3/4" inside that line allowing for the width of the cabinet sides and front and any support members touching the floor, then screwing or nailing the cabinet to the blocks from the side (countersink, fill, add trim) all that good stuff.
On the back side of the cabinets a smaller counter 17" wide is dropped down a couple inches and is supported on the back of the cabinets by a 2" x 15" x 15" block (like a shelf support) cut into a scroll at 45 degrees.
I hope this makes some sense. The Island was not so hard to put down and my granite counter tops were all fabricated so I could attach them with mastic. My unit has electric power and water, so there was some additional preparatory work.