1. Open a blank file. To do that, go to File> New. A box will appear and change the width and height as 500x500
2. Click the Slice Tool
and mark your blank file.
3. Right click on it and choose divide slice.
4. Click the Rectangular Marquee Tool
and mark the box very carefully/accurately.
5. Choose your picture for the first box and copy it then paste it. Edit> Paste Special> Paste Into.
Repeat steps 4 and 5 for the remaining boxes.
6. After you put your pictures, click the Slice Tool to erase the horizontal and vertical green lines. Right click on the file and choose Delete Slices. After that, there’s still that blue/red line on the file’s sides. Go to View> Extras.
And there we have it! You can put some .PSDs or actions to make the image look better:
Just change the blank file size if you want a 1, 2, 3,… etc. pictures edit.