The Indy is the first grab most riders learn. Reach down with your back hand and grab the toe edge between your bindings while in the air. It's the most natural grab because your back hand is already close to the board.
Try it first on a straight air off the S-kicker. Once comfortable, add it to your L-kicker airs and FS180s.
See more here:
Source: Julia Rick · How To Indy Grab - Progression - Cable Wakeboarding Tutorial
Key tips
- Tuck your knees to bring the board up, don't bend at the waist
- Grab between your bindings, not on the nose or tail
- Hold the grab through the peak of the air, release before landing
- Keep the handle close to your front hip with your other hand
- "Board up to the hand" is faster and safer than "hand down to the board"
See a map of all grabs here.