First, create a new text box with A3 paper in PS (that is, the length of two A4s glued together), and then create a new layer with a slogan on it. It is best to save it after setting the location.

Then right-click the text box, select the canvas size, change the width to A4, and there is a 9-square box with 8 arrows pointing inward. Click the arrow in the middle of the left, other arrows will point, and then confirm to save the picture (print); Then the action returns to modifying the canvas size, and then modifying the canvas. Otherwise, click the middle one on the right side of the 9 square grid and confirm. How to save the picture (print) depends on you.