I installed a sink in a 3 1/2 inch butcher block countertop just last month. We could find nothing that would hold it in, such as clips. We ended up using a silicon-based adhesive around the edge and putting a piece of plywood on top of it with a 5-gallon bucket of drywall mud on top of that. Let it sit for at least 4-5 days, and a week is better. No problems so far. It was a copper prep sink, and I spent about 2 hours hammering the edges to get them nice and flat first. Mounting the faucet was also challenge. We ended up counterboring from the bottom to get the nut on.

See link below for basic instructions. Also, make sure the top is supported on all edges.......back, front, sides and middle. Here is a link that might be useful: install

I think you'd need 25" so as to have a bit of overhang, but kitchens do vary. Red oak itself should be a fine material, but not knowing how the one at Menard's is assembled, I can't say if it would work. If you can order a one-foot section and test it out a bunch before the big leap, it could be worth doing.

Yes you're right! So I had the old Carrara marmi and they were getting a new lot in June that would be whiter so I think that ended up being the difference. They said the company switched manufacturers and the whole lot they had received was the off white tone of marmi. It's identical to the first picture! I had no idea there was a new vs old. Luckily they were very helpful and are allowing me to pick out any quartz from the show room and replace it for $300 whichever I choose. I could have gotten the new marmi but I would have to wait until June when it comes in. This felt like a great option to me though as the higher up quartz was not really in my price range at all. So I am happy with that and I got to look through many different styles of white quartz slabs in the warehouse and bring a few home to decide. They are going to replace the whole thing. Now I just have to choose between Cararra Morro and Calacutta Clara!