When our LO was a newborn we used to put her on our softest pillow that kinda “hugged” her a bit so she wouldn’t roll and once she outgrew the pillow we got one of those like infant bed and it has a bumper it helps us maintain a boundary, we have the top of the bed at the top of our bed to ensure our heads are at the same height and don’t have to worry about a blanket going over her. It wasn’t our intention to cosleep, we just did that for naps and we stuck with it