Place the peninsula base cabinets right where you want them and outline their footprint exactly with masking tape, then move the cabinets out of the way. Use a circular saw with a fine tooth plywood blade (or a carbide blade with a lot of teeth) to cut inside the lines set by the tape. Set the saw only as deep as the floor so you don't cut into the subfloor much at all, and stay within the lines. Finish where the saw doesn't go with a sharp chisel or small handsaw. You're basically creating a void in the floating floor into which the peninsula will sit. Fasten the cabinets to the subfloor sheathing with a few screws. Once it is set, install base shoe to make the transition between the cabinet and the flooring nice and clean. The shoe will also cover up chips in the flooring in case the saw blade doesn't cut perfectly...The masking tape will help reduce chipping in a lot of products.