Patterns are a technically difficult kind of calligraphy. It is necessary to observe the balance of letters and decorative elements. Combination of bold and fine lines will make an excellent composition that will look difficult for an unprepared viewer.

This one was made in 30 mins of work without any processing of letter outlines. Maybe later I'll upgrade that pattern and show you completed version.

I used 6mm Pilot parallel pen to draw sketch, scanned sheet, made a image trace in Ai.