To make gin you first need to start with really clean neutral.
Make a double distilled spirit http://www.duckdistilling.com.au/blogpost/double-distillation
Instead of proofing down to 40% you can leave at 95% OR for super clean spirit you can proof down to 40%, carbon filter and then distill back up to 90+%
Heres my Gin recipe
1.75L 94% neutral (90-95% neutral will work)
1 cardamon pod
1.35g grapefruit zest
0.70g lime zest
1.3g lemon zest
1g licorice root
1.4g coriander seeds
.27g fennel seed
0.5g cinnamon quill
All whizzed up in a coffee grinder (except the citrus zest). I soak all the botanicals in the neutral alcohol for exactly 12hours. Then it is diluted with water to 4L (40% abv from memory) and chuck the whole lot in the still.
Discard the first 15ml and keep the next 2L. The first 15mL contains harsh juniper oils Dilute to 45%
Good to drink straight away but the flavour melds a bit over to coming weeks.
Recipe can be scaled up, just multiply everything.