Can't do seated staff pose properly at all

I am currently on Beginner to intermediate program however no matter what I try I find it impossible to do seated staff pose and its variations.

Even when I lift my knees quite a lot I get a strong cramp like sensation on the left hand side of pelvis as soon as I straighten up my back and I have to straighten the knees. However if I straighten my knees I can not keep my back straight at all.

I am not sure what should I do since staff pose and its variations come in a number of videos and are usually quite important.

PS: I do have a belly and on slightly higher side of weight if that matters

Have you tried sitting on a chip foam block? It would give you just a little height but not too much. That could help.

Yes @duke_bball_1 but as I said, I get a strong cramp like sensation in my left side of outer pelvis (where thigh and upper torso meet) when I do that.

I would avoid any pose that causes pain. Childs pose is a common alternative to undoable poses in a class.

I have problems with seated staff pose, and use a folded blanket, block or just find a more comfortable way to sit. I’m at home and no one will see me. I am a smaller person and don’t feel size has much to do with it. If a pose is painful, I modify. I like teachers who offer a variety of modifications or say something like “if it’s available to you.”