Hello, This website has lots of ideas! https://morningchores.com/diy-kitchen-cabinets/
Here's an idea CJ from Lowe's using kitchen cabinets! https://www.lowes.com/creative-ideas/woodworking-and-crafts/kitchen-island-from-stock-cabinets/project
First, you need base cabinets (24" deep and as wide as you want). Lay the cabinets on the backside and measure the inside of the bottom of the cabinet. Cut 2x4s to fit inside the bottom. Screw the 2x4s to the floor, then screw the cabinet base to the 2x4s. That will hold it in place. The countertop should have a 1" overhang all of the way around. If you want to eat at the bar, the side that you want to eat at should have a 12" overhang supported by corbels or some other type of support.