Ok, so I realize the title is a bit of a misnomer.
I’ve never played tennis competitively, but I’m not bad. Hopefully this video helps you see how it can be done with one hand.
Alternate titles I considered:
How To Jump Over A Tennis Net Without Dying One-Handed
How To Sweat Profusely One-Handed
How To Be Dad-of-the-Year One-Handed