It will take testing, but looks to me like for the 4-corners one, you can make two kite shapes, a larger one and a similar one that is nested inside the larger one, and a square who inner dimension matches the outer width of the largest kite…and then from there you’d have to play around in your design software to get the edges to fit nicely with each other, like maybe slightly flat tops and bottoms about the width of you material so there will be a flat edge to glue.
Triangle will be slightly different, but since these things are only holding air plants, I don’t think they need much strength at the top and bottom, so maybe create 3 legs that fit in the triangle and just glue them.