Hi,
You can make your own mold, but it would be easier to start with a ready made mold. Something in our jewelry mold section might fit your needs:
https://shop.resinobsession.com/collections/molds/jewelry
Yes, you will want to do this in two pours. You will see a line, especially if you’re pouring in two different colors, but if you’re using clear resin, the line should be barely noticeable. (You will notice it, but the average person wont know it’s there.)
This video on the resin obsession you tube channel shows you the techniques on how to make your own resin charms:
https://youtu.be/DZPc4y_j7ng