I did propagate saucer magolia by air-layering. You can start air-layering after the leaves appear in the springand active plant growth starts. To be sure, allow 8 weeks for rooting before cutting from the mother plant. You can pot it for the first summer. In the fall, bury the pot up to the rim and put some mulch over the plant for winter protection. In spring you can plant it in ground so it will have full summer to root in the ground.
You can google for air-layering techniques. It is simple.