Wash and dry the lemons well. Finely zest them, taking only the yellow outer peel. Place the zest and sugar in a bowl. Rub together with your fingertips for 2 to 3 minutes until the sugar feels damp and intensely fragrant. Let sit for 15 to 20 minutes so the citrus oils absorb into the sugar. Rubbing rather than simply mixing the zest into the sugar is what actually ruptures the peel's tiny oil glands, mechanically releasing those aromatic oils directly into the sugar without needing any heat.

Add the sliced peaches and 150ml very cold water to a blender. Blend until smooth. Strain through a fine sieve for a smoother lemonade, pressing gently to extract the juice and fine pulp. Set aside. Blending the peaches raw, with no cooking involved at any stage, is what keeps their naturally fresh, uncooked character fully intact — heat would soften and round that flavour in a way that works against this drink's whole fresh identity.

Add the sliced ginger and 250ml water to a small saucepan. Warm gently over low heat until the water reaches a light steaming stage, about 75–80°C, but do not boil. Hold at that gentle low temperature for 5 minutes, then remove from the heat and let steep another 5 minutes. Strain and cool completely. Keeping the water genuinely below boiling, in that specific 75–80°C range, is what extracts ginger's warm, pungent flavour compounds without also drawing out the sharper, harsher notes a full boil would introduce.

Add the fresh lemon juice to the lemon sugar and stir well until the sugar mostly dissolves. Strain through a fine sieve, pressing on the zest, to make a fragrant lemon syrup. The lemon juice's own acidity helps dissolve the sugar while carrying the already-released lemon oils fully into the base, and pressing the spent zest firmly before discarding it captures as much of that flavourful syrup as possible.

In a large pitcher, combine the lemon syrup, the peach base, the cooled ginger infusion, 900ml cold water, and the pinch of salt, if using. Stir very well. Taste and adjust with a little more cold water if needed. The finished lemonade should be bright, peach-forward, lightly gingery, and yield about 2 liters. This final tasting checkpoint matters directly given how much peach ripeness and ginger's own pungency can vary — building in that adjustment stage accounts for that natural variability rather than assuming a fixed recipe always lands at the same balance.

Refrigerate for 20 minutes, until thoroughly cold. That resting period lets the lemon, peach, and ginger components fully integrate together, producing a more unified flavour than serving the drink immediately after mixing.

Fill glasses with ice. Add a thin peach slice and a thin ginger slice to each glass. Pour in the lemonade and serve immediately. Serving right after chilling, rather than letting the pitcher sit out, keeps the drink at its coldest and most refreshing right when it's poured.