Lay the lemons horizontally over the kitchen flat work surface; press each of them under your palms one by one, until all of them get softened a bit. Repeat the process for 1 or 2 minutes.
Take knife and slice all the lemon in half, make sure to cut through the widest part of the fruit i.e. from the centre.
Set a citrus juicer, which has a wedges cone at the top and by pressing against it, you can draw out all the juice from the lemon, while preventing the seeds from going in. Press each sliced lemon half against the cone to squeeze the juice out.
If you do not have a citrus juicer, you can always use your hands to extract the lemon juice. The trick is to let the juice pass through your closed finger so that the seeds can be collected.
Take a blender and pour four glass of water in it. Now add the lemon juice along with a cup of sugar. Blend until the mixture until it becomes saturated. Remember the water should not be cold at this stage as it will decrease the saturation point of the water.
Now fill serving glasses with crushed ice cubes, pour the lemon juice in it and garnish it using chopped mint leaves. Don't forget to sprinkle some black salt over it. Your refreshing summer juice aka lemonade is ready to be served chilled and fresh.