Gather a bright light source
Get a convex lens
Find a cardboard box or similar enclosure
Cut a hole in one end of the box for the lens
Mount the lens securely in the hole
Make a slot or opening for the image source
Place a smartphone or small screen inside the box facing the lens
Darken the room
Adjust the distance between the screen and the lens until the image is focused
Invert the image source if needed for correct orientation
Secure all parts to keep them aligned
Test the projection on a wall or screen
Fine-tune the focus and position for a clearer image