Bend the wire hanger into a square or diamond shape that can lay flat in your container.
 

Pour your bubble solution into the container.
 

Tie a lasso with the string. With one end tied to the frame, the loop should hang inside.
 

Dip the frame in the bubble solution and carefully pull it out.
 

Hold vertically so the lasso hangs into the formed bubble.
 

Using the toothpick, carefully pop the bubble inside of the lasso.
 

The inner bubble will become circular because of surface tension and you should be able to move it around, as long as you don't pop the main bubble.