Best method that has worked for me consistently is using air layering. There are a lot of videos that explain how to do an air layer. IME the best way is to remove no more than half of the side of a first layer, leaving at least the other half to provide water and nutrients to the branch. Sometimes, despite all your most precise work, some maples can be stubborn and take more than one attempt at air layering to produce roots. If your air layer is unsuccessful, you can always remove a bit more for a second or third attempt. Hope that helps, let me know if you have any questions.