Place the sloes, gin and 200g (7oz/1 cup) of the sugar into a large, sterilised jar, and give it a good stir.
Cover and place in a dark place for a minimum of 1 month. I place mine in a kitchen cupboard. Stir it every other day, or as often as you remember to!
At the end of 1 month, taste it, and add more sugar if you think it needs it. I have a sweet tooth, so tend to use the whole lot of sugar. It is drinkable now, but will taste better at 2 months. And more mellow at 3.
To drink, strain through a sieve or, if you like a crystal clear gin, strain though a double layer of muslin or cheese cloth into a sterilised bottle.
Total time does not include the 2-3 months of infusion time. I suggest a minimum of 2 months.