Here is what I have found.
Use melt & pour soap. add a little bit of color, but not too much. Add about 1T or so of grated transparent soap, whatever fragrance oil you like. Melt 1/2 the soap. After all your melting and adding, pour the soap into your molds 1/2 way or a tad less. Let that get a bit hardened...maybe 10 min or so...not too hard, though. Then add your (plastic) whatever you want. Melt and mix the rest of your base and pour over the top of the first part. Remember to place your goody upside down so it shows properly from the top.
Hope this helps.