Lochem, here you go.
this blade is put in a power saw to cut the panel.
It cuts on the downward turn and pushes both cuts down,so no sharp edges.
Using this you need to cut from both faces,then run a handsaw through the foam inner,it also doesn't cause sparks that can stuff the panel finish etc.
These are pics of an esky I made from scrap years ago,you can see angles on the internal and external corners.
The corners of the panels themselves need to be cut at 45 degrees so the angles will cover the cut.
End cuts,cut outs for doors/ windows etc are straight cuts then capped.
The ,tops and bottoms of the panels are held in place by capping channel that suits the panel thickness.
A capping channel is fixed to the floor and up the wall if required,the panels then fitted one after the other,the panels clip together along their edge ( no joiner needed ).
Another channel is fitted along the top to hold it together.
Once the channels are fitted and riveted in place the corner angles are cut to fit between the channels and riveted.
Then fit channels around the openings etc. job done.
Cheers....spog....