Begin by lying on the floor and then elevate your legs, glutes, arms, and shoulders off the floor. The higher your limbs the easier this exercise is. Keep everything straight (no bent knees or elbows) and elevated. Engage your core and hold. This is the hollow body hold.
To work up to the full hollow body hold for one minute, start with small holds of 15 to 30 seconds each. The key here is to remember proper technique and form. Doing the exercise incorrectly for longer does not give you the benefits -- better to hold 10 seconds proper, break, and repeat, instead of holding it incorrectly for 30 seconds.