I used to do this all the time. I had a special-purpose gizmo made to do just that, however, I've lost it.
Basically, put all the chips in a basin of hot water until they soften up, then squish them together into a ball.
I tried heating on the stove and microwaving both, but some ingredient in today's commercial soaps does not allow them to properly melt that way. Instead, they foamed, but did not get soft enough to "squish together" in spite of being hot enough to burn your hands.