I would never lay DD1 down for about 20 minutes after a feed and when I did lay her down it was on a raised mattress and I put her down on her side I also never patted her back to get her to burp, I just lightly rubbed her back, I was trying to not force the burp, just let it come up on its own and she seemed to throw up less if I did it that way. We did lots and lots of tummy time too.