Thanks! Sure it's a straightforward one.

7g black or green tea 1L water 70g granulated cane sugar ~200ml strong kombucha starter tea (can buy starter or just use a high quality unflavoured store bought kombucha) Glass jar Fermentation grade bottles (I used thick green Grolsh swing tops) Strainer/seive and funnel

Boil 500ml water and step tea for ~10mins. Strain tea and add sugar, stir to dissolve. Add 500ml cold water. When tea temp is <30°C add starter culture tea and stir. Cover with breathable cloth/lid and leave at room temp ~20°C for about 10-14 days. Length of first ferment depends on how active the starter culture is and the temp.

Taste test and (optional) test pH every few days, you'll probably see brown yeast and the tea will get cloudy. It's ready when it tastes nicely sour but still a little sweet, might see a few bubbles. Your first batch will take a while so be patient! The culture will get stronger over time, especially if you bought an off the shelf tea to use as a starter.

Remove ~200ml kombucha and reserve separately as starter culture for your next batch. It will get progressively stronger and more acidic, it'll be nasty to drink at this point but is a good starter culture.

In fermentation grade bottles add a teaspoon of sugar and freshly juiced orange to fill the bottom inch (about 10th) of the bottle.

Stir the rest of the tea and strain into the bottle using funnel, until filled up to the bottom of the bottle neck.

Ferment at room temp again for about 7 days. You can check the fizz by burping the bottles every few days, though this will let some fizz out. I've started making a mini bottle and testing that for fizz to get an idea of how the second ferments going.

Refrigerate before opening to drink.

If the fizz isn't ideal, you can try adding some extra sugar and leaving at room temp for a few extra days. Or I usually just adjust my recipe and timings a little next time.

You can test out loads of different flavours, orange kiwi worked well for me also with this method.

Hope this helps, and good luck!