Your feet and ass are connected. I know sounds like a wild idea😜 but, I'm guessing you already knew that. Anyhow, how to untuck your bum with just your feet:
Rock the weight out of your heels and into the ball of your foot.
Make sure your feet are parallel.
Duck feet = tucked bum.
3am rocking baby to 6pm dinner prep; stand with feet hip width distance and parallel and let the weight move from heels to balls of feet. You will feel a shift forward and your ass with move backward keeping your rib cage and pelvis in neutral, now diaphragmatically breathe yourself and your baby into a calm, relaxed state.
Diaphragmatic breathing is a baby whispering trick😜 oh and a pelvic floor must do💃