Archies Thongs are made from a highly specialized form of thermoplastic foam and when heated, the material will become soft and moldable. The following technique can be used to heat mould your Archies Thongs. As this involves boiling water, please take extreme care not to burn yourself.

1. Boil a kettle.
2. Put the flip-flops in the kitchen sink with the arch facing down.
3. Once the kettle is boiled, pour boiling water over the thongs, making sure the arch remains covered by the water. 
4. Keep in the boiling water for 1 minute (do NOT keep in longer than 1 minute as this will can cause the thongs to shrink).
5. Take out and pat dry (of course being careful not to burn yourself with the hot water!).
6. Quickly pat dry the thongs making sure all the hot water is gone and dried up.
7. Once you have confirmed that the thongs are not too hot to cause a burn, stand on the thongs in bare feet (not wearing socks as this will stretch the strap excessively) trying to put all of your body weight into the thongs, particularly trying to squash down the areas where the arch feels too high.
8. It's often good to transfer weight from one leg to the other so that most of your body weight goes through the thong for a period, trying to squash down the areas that are causing you discomfort.
9. Do this for about 3-4 minutes.
10. You can repeat this as many times as necessary until the thongs have moulded perfectly to the foot shape. 

This will heat mould to the shape of your feet, giving you a customized fit.