In a large, heat-proof pitcher/jug, combine the boiling water, baking soda & sugar mix well to dissolve the sugar. Add the tea bags and let steep for 10 minutes (the longer you steep the stronger the taste).
Remove the tea bags.
Add the lemon juice and fill the rest of the pitcher/jug with cold water.
Refrigerate until chilled.
Add lemon slices and ice to a the glasses and pour the tea over the ice and lemon slices to serve.
To avoid potential dangers, if you're not sure if your pitcher is heatproof, prepare the tea in a saucepan and transfer once cooled.