Pull every cheese out of the refrigerator 45 minutes to an hour before serving. Cold cheese tastes like almost nothing, and this is the step most people skip.
Pick three cheeses with different textures rather than three different flavors: something firm, something creamy, and something crumbly. That contrast is what makes a board feel considered.
Place the cheeses on the board first, spaced apart, and pre-cut the firm one. Guests hesitate to be the first to cut into a whole wedge.
Put the jam and the cornichons into small bowls and set them on the board, then fan the crackers in overlapping rows against the cheeses.
Fill every remaining gap with grapes and nuts so no bare board shows, and tuck in rosemary if you have it. Serve at room temperature.