How would go about making oblong saucers for indoor plants?

Hi there, polymer clay can be molded into any shape and after it is baked it will be able to retain water.

I use alot of plastic food containers instead of putting in recycling;look at thrift stores for old casserole dishes, bread plate/dishes,crystal or glass vanity trays,appetizer/hors d'oeuvre dishes. Here is video for pot but you could just make it shallow and any length width,with thinner sidewalls https://www.youtube.com/watch?v=Ze2yBwMsuww here are bonsai pots that would work as saucers https://www.youtube.com/results?search_query=diy+cement+bonsai+pot+ you can make cement ones but they will need sealed so they don't get moisture under/thru them;Paint the inside of the planter with concrete sealer.

Do you buy anything in small plastic containers....I buy ice cream in the plastic buckets and when needing a saucer for my plants, I cut off the side walls until the bottom is about two inches in height. I have painted these before and do work. I have also gone to the nursery and bought different sized plant saucers which look good also. Not sure if you can buy oblong though....only round ones here. How about a platter?

All of my potted plants, inside and outside, are sitting on something I bought at Goodwill. Saucers, soup bowls, casseroles, shallow serving bowls. They are so cheap, easy to keep clean and come in such a great variety. Good luck.

I bought oblong plastic or tinfoil trays from the dollar store and they are perfect to put a few pots on and perfect for watering. You can't over water this way.