Make sure that your cuts are as accurate as possible. If you need to trim areas, you can simply run the knife along the edge. Hold the knife so that the blade bites slightly into the edge. This can be a tedious process so try to get it right the first time.
When insulin binds to the receptor, it is thought to cause a change in shape that is propagated inside the cell, activating the tyrosine kinases. The details are still a mystery and an area of active research.
This means that potassium can't leave the cell anymore, which depolarises the membrane and causes voltage-gated calcium channels to open and release calcium into the cell to trigger insulin release. I don't understand why this happens, because both potassium and calcium being positively charged.