This fixes it instantly every time for me. Ignore everybody else. When you get that cramp start moving our foot in the opposite direction pointing your toes towards your knees and stretch out the back of your ankle. Instant cramp relief everytime.

If you have cramping often like this then maybe dedicate yourself to some hamstring stretches.

Standing up works every time for me. If I want to remain in bed i try to push the bottom of my foot into the bed as if I were standing on it. It often does the job .

yeah that’s what I do. The method described above you is what causes my cramps sometimes