It is recommended you try to get "The Floor Is Lava" achievement later in the game after the Red and Green Zones are unlocked, but it can also be obtained in the Yellow Zone. Start on one side of the map, and set a waypoint marker on a far off part of the map. Try setting the waypoint marker from the south-east corner of the Yellow Zone to the western edge. Choose a tall building to start from, and start gliding. Keep finding buildings to wall run up, charge your jump, and repeat the process. Keep repeating this until you get "The Floor Is Lava" achievement.