Mask the slot with heavy-duty tape as soon as the frame is installed and only remove it as you work your way along the pool installing the liner bead into the slot. A 20-foot diameter circular pool will need about 320 feet of tape.
Cover the sand at the bottom of the pool with a floor padding immediately after laying it down. This provides extra protection for the liner bottom and keeps the sand in place while the rest of the pool is constructed.
Use a pre-manufactured pool cove around the inner bottom edge of the pool to protect against the liner slipping under the frame, instead of using the more traditional sand cove. The plastic foam coves either snap on or are held in place with an adhesive. Without a sand cove there is little to no sand to find its way into the bead track.