Putty!

I wanted to leave this here for anyone who wanted it - a couple of us labs use Crazy Aaron's Thinking Putty in our sample dishes to hold our otos, and were singing it's praises at CARE. You can get it in large quantites in almost any color you want, and in the past when i wrote a note to them they included hardner to refresh my putty with when it gets too soft. 

I love being able to make a water well for looking at surfaces in the same dish as my B&B. Just remember to a) poke a bit of a hole with your tweezers to but the burned oto in, especially if the putty is firm and the oto is small and fragile, and b) put a drop of oil in the hole where you're putting your burnt oto so it doesn't stick. 

https://crazyaarons.com/