I have been told by my local companies that there is not a slap large enough.

Cambria

If you can get a good company that will educate you they can tell you all the sizes available for every type of Quartz. Each one is different and most that are confident can help make something work well for your needs. Also your overhang doesn't have to be exactly 12" to sit at. If they need to take away 2" just to make it fit then that is still plenty of room to sit at. Also there are several granite colors that are not patterns that can work as well. I designed a 10' island with a sueded black granite. Use the help of a good company and they will measure for you and that should be included in their price. Good luck!

You will have to find a granite in solid, or have a seam somewhere. The largest manmade slabs will be 64 inches by 120. inches. There are many quartz with "non busy" patterns that seam VERY well..... solid color granite can be honed. But in a solid surface man made, its 64 x 120. If you are still in "planning" stage versus finished installed cabinetry, you can adjust. Frankly, an island with back to back cabinetry, at a total length of 84 inches/depth of 53 with a ten inch overhang ( 64 x 84 island) solves the problem and your choices virtually unlimited. And may look even better as a less "square" proportion.

Our island is 5 x 10 feet and we had a walnut top custom made. We get nothing but compliments....even from guests who have seen before.