Once you try an angled surface, youre likely not to want to quit, so be careful-- here goes a whole new budgets worth of art supplies!
Your writing arm needs to be free to move, so squished into the La-Z-Boy probably wont be productive.
Hold your fingers fairly straight and write slightly above and just between your thumb and index finger, right where youre holding the pen.
Calligraphy instruction books address hand position, desk position, lighting, paper, you name it--but for some reason, not using the right muscles.
As youve probably surmised, the "right muscles" are not those in the fingers.