Hi,
As I don't possess an iron, but have a toaster, I thought I'd try that.
I'm only making small PCBs at the moment 30X40. I cut 2x 2mm sheets larger than the PCB drilled 4x holes in each corner. Placed the PCB on the bottom ali sheet, then yellow transfer paper with circuit, then a silicon sheet, then the top ali sheet. bolt it all together, but not too tight so it bends. Put it in the toaster for 1.5 minutes. leave till warm, remove and peel paper.
For this simplicity test: Ferric chloride in a chemical glass, heat till near hot and agitate the PCB for 20ish minutes.
Good result!
C.