https://www.sewingbeefabrics.co.uk/how-to-make-a-snuggle-pod-for-small-animals
I know that's not what you wanted but still cute though
It doesn't look too hard. Here's what I would do.
measure two amounts of fabric of how big you want it to be, add an inch. And Cut
Measure the length of it for the sides ( the snuggle part length) add an inch, cut
Measure out how wide you want the snuggle part to be Add an inch, Cut. You will need 4 of these cuts.
Place the design side together and sew the outsides all but one side.
Turn right side out
Fill with stuffing.
Sew up the last side.
Go back to original fabrics place design sides together, sew long side together
Turn right side out
Place stuffed snuggles into fabric up against the sewn side, mark where you want the second side to be, add a half-inch, take stuffed snuggles out sew down the line.
Place stuffed into the holders and there you go.
And I just kinda went off of this as how I looked at it and figured out with my very small knowledge of how to sew but my many years of watching my grandmother. You may have to tweak it some as you actually get into it. But now I think I may make both of these. the pod for their houses and the snuggle bun bed for their carriers for vet trips.