If u see it tilted towards the bottom, try to look at it from bottom to up, and if u see it bottom to up try to see from the top to bottom (idk if that makes sense but thats how i find i can see them, tho ur brain quickly adjusts to the “default” whichever u saw at first), also blink…
How I manage to do it is by changing my own perspective. Instead of thinking “I’m looking at a cube”, I focus on parts of it. For instance, at the very center of the drawing, there is a small square with nothing else overlapping it. That small square has two triangles touching it’s top left and bottom right corners. By trying to perceive those 3 figures as the main part of it, I was able to stop seeing any depth.
Another way is to turn the entire drawing around. The absolute top right 90° corner and the absolute bottom left 90° corners can be viewed as one aiming up and one aiming down, or as left and right. You essentially turn the drawing into a rhombus in your mind with extra details