Undermounting a sink is a difficult thing to do in Sketchup. Cutting the hole in the countertop and getting it to the correct shape of your sink can be a difficult task. This is something that I do on a regular basis, so to make things easier, I have created a special dynamic component that will automatically cut, and size the hole, and place the sink for you!
There are a few steps you have to take to prepare your countertop first, which I cover in this video. Using this technique will save you time, and much frustration!