I've been using these most of my life.
Eagle Claw LL1 & LL2 Leader links. They are quick, simple and secure. Have always been surprised by how little force a hinge points which induces cracking.
When you tie the knot for the fly ine, seal the end with something. When feeding the leader threw, feed the tippet through the center and then pull the whole leader through to the butt; tie the knot, trim and pull tight.