Can I Pay a Part-Timer for Additional Piece Work?

Can I pay a current W-2, 1099 employee for piece work separately from his main part-time hourly responsibilities? This work would be blog articles to be written away from the office with no direction, and then we'd decide which articles to buy. Is there a better way to handle this? Our business is in Oregon, in case our state is pertinent.
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Based on your description of the nature and arrangement of the offsite work, I believe that you can do this. You must be careful that the employee is not working more than 40 hours a week doing both "jobs" since the Fair Labor Standards Act requires that workers be paid time and one-half of their aggregated average hourly rate for hours worked over 40 in any single work week.