Turn the stool seat upside down and place it on a flat work table. Measure the diameter of the seat by stretching a tape measure across the width. Divide the width in half to locate the center of the seat and draw a pencil mark there.
Place a straight edge on the center mark and draw a line all the way across the seat. Draw another line perpendicular to the first so the seat has four quadrants.
Measure 1 inch from the edge of the seat along each line and draw an "x" to represent the positioning of the four legs.
Place one of the legs on top of an “x” and trace around it to create the actual outline of the leg. Repeat the process at each remaining “x”.
Insert a 1/4-inch drill bit into a drill and place the drill against the center of each leg circle. Drill all the way through the seat at each location until the bit extends out of the other side. Repeat the process on each remaining leg mark.
Drill a 1 1/2- to 2-inch deep hole in the center top of each leg to accommodate the screws.
Insert four 3-inch long screws through the top of the stool seat and place the seat so the screw threads face up.
Align the holes on the stool legs with the screws and turn the legs clockwise until they are tightly against the stool seat and no portion of the screws remain exposed.
Turn the stool over and press down on it with your hands to ensure it does not wobble. If the stool wobbles, tighten the screws from the top using a screwdriver.