Here's what I came up with. Now, don't laugh.
I use Schick Intuition (best razor EVER for sensitive skin, btw) and the replacement blades come in little plastic containers like this. I kept a few of them because I KNEW I would end up using them for something at some point.



Yeah, you know where I'm going with this.
Now get your eyeshadow sample.

I just put the cup down in the sink and carefully poured the eyeshadow in. A lot of it sticks to the sides and corners so I had to get a brush to scrape the rest of it out.

Now just label it! I used a piece of tape so I can re-use the container when I run out of this color. I will probably try and get a bit more creative next time haha

Tada! No more messy-ness. :)I hope this was helpful, and I leave you with this adorable picture of my dog Halo.

Have a great evening!