Im planning to convert a spare room I have in my house into a messy play room, so far I've got an inflatable pool set up with some plastic sheets in the mail to protect the carpet. but i also plan to get some cupboards set up to store anything non-perishable like cake batter and sauces
if you guys have any tips or ideas, please let me know
Last time I did that (well, honestly the only time) I made a 4" tall frame out of PVC pipe that ran around the edge of the room. That gave me something to attach tarps to and provided an edge that things wouldn't run off of and onto the carpeting. For the top I hung a bunch of narrow 'decorative shelving' fairly high up so tarps could be easily attached.
Worked pretty well and when we moved the shelving stayed and just looked like knickknack storage, no one said a word.
I used a large inflatable pool when I had my setup, it would not hurt to have plenty of extra towels on hand for your trip to the shower. Also recommend a smaller inflatable pool if you want to do larger messing, it served as a mess holder and when clean and empty I stored made-up pies in it which was nice cause if they spilled it was no big deal. I made sure that the big pool was big enough for me to be able to lie down in it which was nice. OO and a small folding stool is a must-have prop if you ask me.