Joseph, If my over-hang will be around 15" on the long side and 12" on the short side I will either need corbels or brackets - and the top will need to be screwed into the cabinets, right?

This is what the island looks like without the top without the side panels attached. I was thinking I could run wood screws up through the holes in the stectchers but I feel I still need support brackets for the back where the over hang will be.

The back of the island is where the seating will be. I would love to just lay it on there, glue it down and call it a day but that just doesn't seem safe.

My husband says that if we use brackets that attach to the top of the cabinets to support the top it will raise the top too much and we will have a gap.

I have tried to find a video but I am not having much luck.

Use some L brackets. Attach one leg to cabinet and one leg underside of countertop.

Use the screws; no brackets are necessary.

Better be sure those cabinets are securely attached to your subfloor too. Doesn't sppear that you’ve done the electrical yet, and that's much easier to do before the top goes on. Do that first.

Corlett is right, dabs of a decent adhesive should be enough. We use Power Grab. However, it there is a chance that all 300 lbs of Uncle Wilbur will sit on the cantilevered end, screw two screws at the other end up through the cabinet frame into the countertop.

With a withdrawal force of about 150 lbs for each screw driven into a close grain hardwood, the screws and mastic should hold any reasonable amount of weight. Still, I would not stand on the cantilever to change a light bulb.

Rory - any pictures of the finished Ikea butcher block island top? Would love to see!