I have an old Old Spice Shaving Mug that I want to load with soap. Most cakes of soap are too large to fit into the mug without trimming or cutting the cake down to size in order to fit flat into the bottom of the mug. I don't know if anyone else has faced this issue and found a solution with a soap puck that fits well into the mug, or if there is a soft soap that works well. I welcome any suggestions.