Rinse off your sloes and if you have the patience take off any stems that may still be attached
Pop your sloes into the freezer overnight to ensure any underripe berries get a "frost treatment"
In a large sterilised jar (I use a 2 litre jar from le parfait) place your sloes, cover with sugar and finally a whole bottle of gin. Give it a good stir
Your gin needs to remain in contact with the fruit and sugar for 3 months in a cool dark place (like at the back of a cupboard) If you think of it, you can give the jar a good shake from time to time.
After 3 months, strain off the fruit and bottle your sloe gin. This is perfect in a cocktail or even very simply over ice.