Whatever you come up with keep in mind that there has to be shade/shelter and water provided. A snake can overheat in direct sunlight even on a cool sunny day.
Also if you aren't going to watch them 100% of the time then it must be very secure.
Possibly converting a rabbit hutch ??? Would need to change the wire to nylon screen to make it escape proof. Plus nylon will be easier on the snake if it is nose rubbing.
PS: I apologize to all Floridians for thinking that Karl's pic had to be in FL. LOL A quick image search shows that it is in Seattle WA. :face_palm_02::laugh::crazy02: