This is how we starting build towards the full Hollow Body Hold.
Bend your legs, keep them together and raise them towards you, knees are over the hips.
Point your toes. Straight arms are extended in front of you.
Reach forwards, lift your shoulders and upper back off the floor, feel your core engage. You should feel tension throughout your whole body.
Keeping reaching forwards, core shortened (think about bringing your chest towards your hips) squeezing the glutes, hold for time.
Do not allow your core to lengthen, or back to arch. Rest anytime your shoulders start to drop and you lose core engagement.