1st variation: Lie on your back, curl up your knees toward your chest, and rock back and forth, while interlocking your legs into the triangle. Understand how to use your body as momentum.
2nd variation you will sit up on one foot and one knee and bring your hips up and forward. Rock back, gather some momentum, and on the way up, cross your legs in the triangle position, planting one foot on the ground, and push through your heel simultaneously bringing your hips forward.
3rd variation: Gather more more of your momentum to actually stand up on the one planted foot, so rocking back, hips come forward with body on knee and foot, and then stand up using the planted foot.