SOLARSTILL BOX is a low-cost, off-grid water purification system designed to provide safe drinking water for communities with limited access to electricity and water-treatment infrastructure. Using solar distillation, contaminated or saline water flows through stepped channels where it is heated by the sun, evaporated, condensed on a transparent cover, and collected as clean water. Designed as a lightweight flat-pack structure, the system can be efficiently transported and assembled locally in about 20 minutes using simple tools and locally available supports. Without electricity, replaceable filters, or complex maintenance, SOLARSTILL BOX offers a simple and accessible approach to decentralized water purification. At an estimated cost of $20 per unit, it can produce approximately 6–10 liters of clean water per day and up to 30,000 liters over a 10-year lifespan.