How did you get the melting so even? I just started Perler bead art recently, and of the three things I made so far, two were melted so the holes vanished and the beads were square and the other was completely uneven.
I think it mainly depends on your iron. I have set mine on "wool" which is a medium heat setting. After ironing for some time it's even too much heat and I have to set it down to "silk". I hope that helps