Mine were also day old shipped chicks. They brooded outside with a MHP in 20°F weather. I had cardboard around the sides of my dog crate to keep breezes off the chicks, straw underneath and on top of the pad. I bent the MHP frame so it was low enough for my bantam chicks to snuggle underneath...
I like it @EarthAlabama !
I used vinyl coated fence pieces, the Sunbeam heating pad, small bungees:
The fencing could be bent higher as the chicks grew.
Then I covered it with a pillowcase. The case drooped so I used binder clips and some zip-ties to keep it against the heating pad.
I used...