Measure the length and width of the ceiling and obtain a fabric piece that's at least 1 foot longer and 1 foot wider. This allows the fabric to drape from the ceiling, covering the uneven effect.
Place a ladder in one corner of the room and use a staple gun to attach a fabric corner to the ceiling corner. Move the ladder to the opposite corner and repeat. Continue until all four corners are held in place.
Add staples around the perimeter of the ceiling for security. Add staples at even intervals throughout the ceiling to create small sections of draped fabric or leave as-is, depending on your preference.
Measure the dimensions of the ceiling and obtain enough fabric squares to cover double the area.
Cut pieces of fabric into squares at least 3 by 3 feet for manageability. This also allows you to use different fabric patterns or colors. Use one giant piece of fabric as an alternative.
Place a ladder in the center of the uneven ceiling. Hold the fabric and staple directly in the center. Gather several inches of the fabric toward the stapled section to form a small, hanging bunch. Staple the bunch in place. Continue the process until the piece of fabric is completely attached, forming a series of the hanging bunches. Let more fabric hang down, or bunch up more on different ceiling sections depending on the unevenness. Repeat until the ceiling is filled.