Open the hips, stretch the quad, breathe into it.
Keep both knees pinned at 90 degrees, ease in slowly instead of forcing the range.
From the 90/90 seat, squaring your chest over the rear thigh and lifting your hips slightly puts a stretch down the front of the trailing hip and quad while the front hip sits in external rotation. It is a two-for-one, hip rotation from the position itself plus a quad and hip flexor stretch from the lift. That combination is hard to find in one bodyweight hold.
The couch stretch bends the rear knee against a wall and hits the quad more aggressively, while the shin box version stretches the quad and hip front from a seated rotation position. The shin box is gentler and adds hip rotation work the couch stretch does not have.
Widen the angle so the knees bend less than 90 degrees, sit on a cushion to unload the hips, and ease into the lean gradually. The position should feel like a stretch in the hips and thigh, never pressure in the knee joint.
The hip lift is what deepens the quad stretch, but it is optional. Start by just squaring your chest over the rear thigh, and add the lift once the base position feels comfortable.
