Best DIY method of building a sill pan for sliding glass door?

[REK]

I need to install a sill pan for a sliding glass door that was installed without one... What is the best approach? Fabricate one out of metal (I have read that in the cold, metal can conduct the cold towards the inside and cause condensation)? Vinyl? Is using flashing adhesive to seal the overlapping material when forming the ends of the pan? Are the "adjustable-length" pans any good?

Thanks for your advice.

 

[nealtw]

The pan is only adding the lip at the inside of the window that was not there when we did the flexible. With windows they solve that by adding a 1x? just inside where the window will go so the flexible can wrap up like the hard pan does. There is no reason why you could not just add a small flashing for the inside of the door and use a flex flashing to complete it.