In Photoshop you can place guides (dragging them from the ruler bar) to denote the slices of the full-sized image. Then select the Slice tool (it is in the same palette as the Crop tool) and select "Slices from Guides" in the toolbar. Use the Save For Web (Legacy) export option and configure the image format and slice options. You will get a folder with the slices in it.
If you plan on printing each slice to a certain size, you would want to upres the original file to the proper size and resolution (in PPI) so that each slice conforms to the desired output size. For example, let's say you will want 3 slices wide and 2 slices tall and each slice will be a portrait-oriented 8"x10" and you want 300 PPI prints. Then the total dimensions of the unsliced file should be 24"x20" - if you want to print at 300 PPI, then the resolution of the upres-ed image must also be at 300 PPI before you slice it, i.e., the original image needs to be 7200 pixels wide [24 inches x 300 PPI] by 6000 pixels tall. Otherwise you will have to upres each slice individually.
kirk