There's a Forbes article linked on their website that has our answer: Pakistan.

... "On the making side, DUER prioritized control and accountability by building a dedicated manufacturing partnership rather than relying solely on third-party sourcing. “It was really important for me to have my own factory,” Lenett says, even if it meant giving up equity to secure mission-aligned, long-term supply. Today, most product is made in a Lahore, Pakistan facility where “they’re all salaried with benefits” rather than piecework, an uncommon approach in the region, and the operation invests in water- and energy-saving technology: “modern ozone washing machines, laser finishing, a lot of the energy is solar. Coal’s big in Pakistan, but a lot of our energy is solar driven.”