with each one about 1/8" from the edge. Just make sure you surround each screw hole. I wouldn't worry about trapped air. The butyl will give and take a bit and air compresses.

On this white skeg below my boat I put one strip all the way around the perimeter, about 1/8" from the edge, and surrounded each of the 8 bolts with butyl so that it would squeeze out the holes when tightened up. The butyl squeezed out the sides a bit all the way around, and I cut the excess with a knife. It's submerged 6 months a year but it will stay dry inside the boundary.