This next part is really annoying. When I bake the these shapes in the oven the solder in the open end melts and resets in a new shape, blocking the entrance to that hole which stops you connecting the second half of the frame.

My way around it is to heat it up again on the stove in a very specific spot and try to extract the excess solder. Without destroying my cooker. I tried to put foil down to protect the hob but it completely blocked the heat.