In its simplest form, the idea was to fill the Christ child's manger-crib with plenty of soft straw and warm hay so that he would be warm and comfy.
To add a straw or a piece of hay daily, we did one good deed that day. I cannot remember when we began each year. I suspect it was with the beginning of Advent. The more good deeds we could do, the softer and better the pile of hay would be to cushion the baby Jesus in his wooden crib.
I think that it's still not too late this year for me to begin adding some filler to that manger.
Lord Jesus, thank you for reminding me of this sweet tradition. Help me by whispering to me whichever good deeds you need for me to do each day.