You just need to hit the opponent with certain assists while the Lunar Phase is going. If done properly, they’ll groundbounce even though you started LP mid-combo.
And best of all… they don’t have to be in the corner for it fully connect!
Assists that work that I know of:
-Firebrand’s B Assist.
-X-23’s B Assist.
There’s probably a lot more. The one downside to all of this is that the assist needs to hit while LP is still going, which in most cases means that you have to call the assist before attempting a hit-confirm, which limits the usefulness of this.
Example of combo:
Call Assist, s.S, s.H, Lunar Phase, s.S, Standard Air Combo into High Time xx Dimensional Slash OTG or relaunch with other assist.