The baby should sleep. Ours was six weeks, when I made the footprints. I have it .... laid on his stomach on the bed so you can make the handprints very good.
Then knead the impression material and divide by 4. Grab a wooden or breakfast board in a freezer bag and roll out there, the first of 4 servings. Then lay the boards with the rolled mass on the sofa and press the baby's hand with fingers spread under some pressure in the mass. Then cut the footprint with a big kitchen knife. Finish is the footprint!
From the sections of 4 imprints you can still make one or more prints 2. So you have even gifts for Grandma and Grandpa! :-)
Absolute buy recommendation! Great memories!
The only drawback: The packaging and the framework smell very strict ... somehow ... possibly chemically. by spray paint from the frame ... have him put down outside to evaporate ... then go.