Most sinks are supplied with a cutting template (usually printed on the cardboard). If not, make one or use your sink upside down (as here).
Center the template on the artboard, and then accurately mark the path. Inside the path, drill a hole of sufficient diameter to pass the blade of the jigsaw. Choose a blade adapted to the material, with fine teeth. Set the machine to medium speed. If the tool has one, disengage the swinging motion to limit splinters. Saw along the path, without forcing the saw (regularly remove sawdust).
If the worktop is laminated, mark the pattern on the underside to make the cut on that side. The jigsaw works upwards and produces shrapnel "out". On a solid wood panel, the chips are less consistent and will be covered by the edge of the sink.
Cut the work plan
Cut the worktop to size with a circular saw guided against a ruler or a clamp clamped by clamps. If the song is visible, sand it finely.
Mark the location of the sink
Locate the location of the sink (consider the location of the faucet). Draw a line parallel to the back edge, then another perpendicular with a square.
Post the plot and drill
Carry out the template layout by taking these two perpendicular lines as the base. Drill a hole inside the path to insert the blade of the jigsaw, then make the opening.