Start from the Straddle handstand with 5 fingers support series: use 1-finger support while learning; advanced athletes can simply tent and lift the hand.
Lift the arm and hold it in the same plane as the bottom leg.
Keep both shoulders shrugged ( Shoulder elevation ); do not let the Upper trapezius relax as the hand leaves the floor.
Balance with the fingers and forearm, making frequent small corrections.
Keep the hips slightly bent for a wide, stable Straddle position , legs tense but free to correct.
Form tips
Do not grip the floor hard the whole time: keep the wrist and fingers engaged but relaxed enough for quick corrections.
Experiment with small changes in arm position to learn what you can balance.
Expect a long learning curve; consistency with the basic drills speeds it up.