Collect all your materials and tools. Measure your space one more time to confirm the 20-inch width requirement. Mark your wood pieces for cutting.
Cut your 1x12 pine board to create a tabletop that's 19 inches wide by 36 inches long. This gives you a little wiggle room while maximizing surface area.
Cut four equal pieces from your 2x2 lumber, each 16 inches long. This will give you a standard coffee table height of about 17-18 inches once assembled.
Cut four apron pieces from remaining 2x2 lumber: two pieces at 32 inches for the long sides, and two pieces at 15 inches for the short sides. These will connect the legs and support the top.
Sand every piece starting with 120-grit sandpaper, then finish with 220-grit. Pay extra attention to the tabletop surface and round over any sharp edges for a polished look.
Attach the apron pieces to the legs using wood glue and screws. Create two end assemblies first (leg-short apron-leg), then connect them with the long apron pieces. Pre-drill holes to prevent splitting.
Flip the base upside down, center the tabletop on it, and secure from underneath using screws through the apron into the tabletop. Use 1.25-inch screws so they don't poke through.
Apply your chosen finish — stain for color, then polyurethane for protection. Apply two coats of poly, sanding lightly with 220-grit between coats. Let dry completely before use.