Never made it before, but the sloes are also cropping well in the hedgerows this year!
Combination of recipe here and input from a friend who makes sloe gin annually:
Fill a container a third-half full of washed and pricked sloes - I am using a 4l plastic bottle (used to contain water) - add some sugar (about 500g) then fill with gin. Agitate bottle once a day for a week then once a month for 2-3 months. Decant! Making it end of Sept/start October means it should be ready to drink this Christmas.