We want to cover the sealing surface of the watch without getting any adhesive into the (3x) spring holes.

Tiny springs go in these holes and make an electrical connection between the watch case and bezel.

If you want to improve the waterproofing of the finished product, you can line the entire perimeter of the case with Sugru, but it could reduce the Bluetooth range. I haven't tested this myself but will the next time I repair another of these watches.

Lay out small strips of the rolled Sugru, until you've covered the perimeter of the bezel. Give the Sugru a light smush into the bezel to keep it in place.

I put a thicker coat of Sugru than necessary on this watch, but we will address that later. You should roll the Sugru out a little thinner than I did.