This is quite a fun trick for you guys to play on your friends. The dice appear to be fair, but land on a certain side much more often than any other side.
1. Place the dice on an oven tray.
2. Turn the dice so that the numbers you want to land on are facing upwards. In this example, the numbers 5 and 2 would appear more often than any other.
3. Cook the dice in the oven at 250 F for 10 mins. The plastic inside the dice melt, making the bottom heavier when they cool down again.