The Cossack Squat is a form of a mobility where you descend with the most of your weight on the squatting leg while keeping the other leg straight and to the side with the toe facing the ceiling. The arms are going to be in front of us and they will have a role of counterbalance. The back should be straight during the movement, but you can lean forward with your upper body.
As a beginner you probably won’t be able to hit full depth of the Cossack Squat, but don’t stress about it, just work your way down trough repetitions. Try to hit depth with every repetition and hold the bottom position for 3s each repetition. Make sure the heel is fully on the ground and don’t let it raise. With the elevation of the heel you won’t be making the same mobility gains because you won’t be stretching out the hips, hamstrings and ankles.
To make the exercise harder you can either add weight or to try sitting down.
With adding weight you can focus on progressive overload. The weight can also help you reach a greater depth
Lowering your straight leg to the ground and trying to sit down on the ground will demand even more mobility and this can be a challenge. In the bottom of the Cossack Squat sit back down and then try to get back into the bottom position and squat back up. Hands can be used to assist you. (Holding onto a rail or using a weight with straight arms to help you get up).