Just like the Basic Front Plank, you can do the Side Plank from your forearm or hand. Doing the Side Plank from your hand is harder and requires more core and shoulder stability. Stacking your feet on top of each other instead of having one foot in front of the other also makes the move harder.
Beginners will want to start with a Side Plank from their forearm and knees or knee (you can bend your bottom knee and have your top leg out straight instead of stacking both knees on top of each other).
To do the Basic Side Plank from your forearm, set up on your side and prop yourself up on your forearm with your elbow right below your shoulder. Your legs should be out straight. You can either stack your feet or place your top foot on the ground in front of your bottom foot.
Then, driving through your forearm and the sides of your feet, lift your bottom hip up off the ground as high as possible while keeping your body in a nice straight line. Squeeze your belly button in toward your spine and keep your glutes tight. Do not let your chest rotate forward toward the ground or your top hand touch the ground. Keep your top hand on your hip or reach it up toward the ceiling.