I wanted squares on my nails and originally planned to paint them on, but they weren't perfect enough so I cut squares from electrical tape. It ended up being much easier. A top coat is a must since the corners will snag on things. I like the look of the matte tape so I used a matte top coat, but it looks nice with a glossy one, too.
OPI in My Boyfriend Scales Walls
NYC in Matte Me Crazy! Mattifying Top Coat