Slice the ends of off your cucumbers and discard, then slice the cucumbers into coins, roughly 1.5cm thick.
Sprinkle salt on a plate and cover the plate with one layer of the slices of cucumber. Sprinkle salt on top of that layer then add another layer of cucumber on top. Continue salting and layering your cucumber until all of your cucumber has been salted. I ended up using two plates. Leave for two hours to macerate.
Whilst you are waiting on your cucumbers to macerate it's best to make the pickling brine. To do this it's really easy - simply add the vinegars, water, sugar, garlic slices,, mustard seeds and peppercorns to a pot and heat gently over a low heat, stirring until the sugar has dissolved. Once you've done this leave this mixture to cool.
After about 1 hour and forty minutes sterilise your jars and lids. To sterilise jars see this guide to sterilising jars. Once your two hours is up rinse the salted cucumbers and pat dry with clean tea towels.
Place the cucumbers into your jars and evenly divide your fennel flowers between the jars. Pour the brine over the cucumbers and fennel, leaving just half a centimetre from the lid of the jar. Seal and leave in a cool dark place for 48 hours at the absolute least, but preferably a week. The longer you leave it the greater the taste, so patience really is a virtue!
The jars should keep for around 3 months unopened. If you want you can place your sealed jars in a bath of boiling water for 5 minutes to process them - this should mean they will keep for around a year, unopened. They do soften a bit using this method.
Once opened, keep your pickles in the fridge and use within a fortnight.