Sand all the dinner table components: two side aprons from 1-by-4 lumber at 66 inches and two end aprons from the same lumber at 32 inches; five tabletop supports from 1-by-2 lumber at 32 inches; three 1-by-12 planks at 70 inches to make the tabletop and four legs from 4-by-4 lumber at 29 inches. Use a sander or sandpaper and a sanding block.
Make the aprons into a rectangular frame. Square off the corners with a square and set them in a band clamp to hold the shape. Drill two countersunk pilot holes sized slightly smaller than 2-inch wood screws through the side aprons into the ends of the end aprons. Screw together with 2-inch wood screws, then remove the band clamp.
Slot the five support planks in between the side aprons, evenly spaced along the length and flush with the bottom of the apron frame. Secure in place with two 2-inch wood screws in each end just as you secured the apron frame.
Bead glue along the edges of the tabletop planks and fit them together side by side to make a single tabletop 36 by 70 inches. Use band clamps to clamp the planks in position while the glue dries. Turn the tabletop right side down.
Apply glue to the bottom of the apron frame and supports. Center the apron frame over the tabletop, with the supports touching the tabletop. Use G-clamps to hold the frame down onto the tabletop while the glue dries.
Pre-drill two countersunk pilot holes through the support planks into each tabletop plank; six holes per support plank. Secure the tabletop to the frame by screwing in 1 5/8-inch wood screws.
Insert a leg into each corner of the apron frame and use G-clamps to hold them in position. Pre-drill two countersunk pilot holes through each side of the corner into each leg and secure the legs with 2 3/4-inch lag bolts.
Turn the table over and finish with your choice of wood finish. Full paint creates a more modern look, or you can leave the top wood and paint the rest white for a chic country look. Classic dinner tables would have a stain or varnish, or use a wax finish for a more rustic feel.