Combine the hot water, sugar and salt until the sugar and salt are completely dissolved.
Pour the sugar water into a cocktail shaker or an old jam jar, then add the soju, lemon juice and a few scoops of ice. Place the top or lid on the container, then shake until the outside of the container is cold.
Place a scoop of fresh ice in your serving glass. Strain the drink (leaving the ice behind) into the glass, then serve!
Granulated sugar can be substituted for honey or agave.
Can be made ahead; store in the fridge without the ice for up to a few days.