STEP 1: First, Take your cardboard, then trace the bottom of your jar.
STEP 2: Now, take the shape you made with the pencil and the jar and cut it out with your X-Acto knife
STEP 3: Now put the shape you cut out in the jar by folding it slightly so you can stick it in the jar.
STEP 4: Now glue the cardboard to the inside of the jar, on the part where the jar goes "inwards" slightly, near the bottom
STEP 5: Now remove the labels
STEP 6: Now spray paint the jar with any color you like, except you have to leave at least one side open as a "window"
STEP 7: Now place a Lego display piece in the center of the cardboard. Now you are ready to place legos in your new holder!