Firstly this was the first door I ever attempted and everything was done in my garage using pretty much standard electrical hand tools.
At the time I had just had Australian Jarrah
flooring laid in the house to replace the horrible carpet in our first house.
Thankfully I had some lenghts of flooring timber already in the garage (complete with tongue and groove) I knew I didnt have enough but luckily my friend who did the timber floors always ends up with various cuts of hardwood laying around so I managed to collect enough to cover the job.
So I started with a sheet of Marine Plywood that I cut to the right size (the dimensions of the frame i the thickness of the boards (12mm) around the whole thing (so I could frame it with jarrah too)
To cut it to size all I used was a standard drop saw.
After cutting the sheet to size I cut the groove away from the first board and top nailed that to the plywood (note at every step I used flooring glue to secure the timber to the plywood)
After setting the first board I used what australians call a 'secret nailer' basically it's a nail gun that fires small nails at a approx 45 degree angle through the tongue of the timber.
Using one of these means the end result is that no nails are seen except for the first and end piece that are top nailed.
The picture attached is when I had laid a fair few boards and cut the hole where the dual glazed glass was supposed to go.