Hot Water System

i have to make it at school so i can’t make anything else (wooden box etc)
i need to heat 4 litres (a gallon) of cold water in the space of roughly an hour and a half using just solar energy

could i please get an easy step by step guide for this?
how will i make the water circulate through the tube etc? (this was just an idea given by my teacher, the solution doesnt have to incorporate this)