Establishing four square surfaces on a wood board may be performed in two or more steps according to the available machines and your way. First of all we need to flatten the wide side of the workpiece to get a reference surface then squaring one edge. Planer-jointer is probably the most convenient tool to work fast and accurately get the first right angle. Click on that link or in the below drawing to read about planing and edging with a planer-jointer.

But up to 100mm I most of time use this technique on the table saw so that squaring the two first sides. I am under the impression I get a better control on waste.

Finally we can't escape the planer-thicknesser in getting wood flat and parallel albeit I always prefer the table saw to cut edges.

Here is a way of squaring panels in one work cycle with the help of the wagon carriage