Sleep on the bed sideways?

Is side to side or sideways what you’d say?

We slept side to side/sideways on the bed so we could all 3 fit.

Is it correct to start the sentence with depending? Is diagonally correct?

Our 3 year old sleep in our bed. Depending on how he like to sleep, we position ourselves. He sometimes want to sleep diagonally or sideways.

Thank you