Put the linden blossom, lemongrass, peeled piece of ginger and orange juice in a container, cover and let steep for 24 hours.
Then strain and squeeze out the linden blossoms. Add the liquid sweetness, the citric acid and the gelling powder to the juice, stir everything well and let it boil for about 5 minutes (according to the instructions on the packet of the gelling powder). Fill into glasses while still hot.
Instead of the jelly powder (for diabetics or the calorie-conscious) you can of course also take normal jelly sugar, but then omit the liquid sweetener.