New build a fast road bike for myself. 58cm Columbus spirit frame with a a integrated seat post (ISP), that you sometimes see on carbon bikes.
First I layout the full size drawing on the flat surface and check the parts are call correct and fit.
Next I start with the head tube, ream it.
Then assemble the head stock with the forks and stem to check fit. Then i silver solder in the integrated headset cup and drill a vent hole.
Next time, fillet brazing the head tube and frame ends.