Just a quick note, when using this method it is best done in the warm to allow the air bubbles to escape while still runy.
Or you get opaque windows.
The smaller one is 5.5mm opening and the larger one is 13mm opening.
They allow light through but are totally waterproof.
With practice it is possible to get a clear glazing.
All you have to remember is to use a plastic or film or even a silicone mat so that it is possible to lift off once set.
A £1.00 bond together set will do at least a hundred portholes up to 10mm diameter.