One of my projects this year is resin coasters.
I have been saving bottle caps all year for this project, it helps that my friends drink a lot of interesting beer.
I bought these resin molds online for pretty cheap (don't cut corners here, the chemical reaction as the resin hardens will cause it to stick to or melt your mold if you aren't using one designed for it).
The next step is to spray on a mold release and let it dry (if you don't let it dry all the way the mould release will float to the top of your resin when you pour it in, where it will be useless)
Next I pour out the right amount of resin
and mix in the hardener. I do this in disposable cups with disposable spoons to make my life easier.
I pour a small amount of resin into the molds, arrange my bottle caps on top, check underneath to see that they are straight and then fill the molds the rest of the way.
The resin takes a few hours to harden all the way through, and then I pull them out.
And as an added bonus I am becoming much more comfortable and skilled with using resin (which is really great for fake drinks, but I have messed up multiple times in the past when I didn't measure parts correctly).