Gather your supplies
900 x 900 x 18mm MDF (2); 2-part filler; oil-based sealer/undercoat; gloss enamel; 100-125mm-high castors with brakes (4)

Here's how
Step 1: Carefully align, glue and screw MDF sheets. Smooth any proud edges with a plane.

Step 2: Use a 2-part filler to fill any imperfections around the edges. When dry, sand smooth. Round over top edges and corners enough to remove sharp arrises, then paint with a water-based sealer/undercoat to seal the surfaces. Paint the underside as well, just in case drinks spill and run down the edges and under the table.

Step 3: Sand smooth, then paint with 2 coats of gloss or semi-gloss enamel in the colour of your choice. Sand between coats.

Step 4: Upturn table on a drop sheet, then screw on 4 castors, centred 100-125mm in from each corner.