A fenestration unit includes a first glass unit, a first panel frame, a second glass unit, a second panel frame, a sill flashing, and a frame. The frame includes a header, jambs, and a frame sill including a first track and a second track. The first panel frame and the first glass unit are slidable along the first track when positioned in the frame. The second panel frame and the second glass unit are slidable along the second track when positioned in the frame. The sill flashing includes a base extending under the first and second tracks and a wall extending upward from the base to inhibit moisture intrusion through the fenestration unit. The frame sill is removable from the frame without disassembling the sill flashing, the jambs, and the header.