If a company only has one employee besides the owner, must they file the paperwork etc for an alternative workweek? The employee I am thinking of supposedly works 4/10 M-Th but is continually called in to work F, S, Su. No OT is received for time above 8hrs M-Th but nothing has been written and submitted.

An employer can not self-impose on Alternative Workweek Schedule (AWS) upon it workforce -- even if the workforce is comprised of just one employee. Absent a legally-adopted AWS, an employer is obligated to pay its non-exempt, hourly employees (or single employee, as the case may be here) overtime premium pay when he/she works more than 8 hours in day.