I had a black mat set for the bathroom and didn’t like the toilet seat cover so that got me thinking. I could use the black and also bring up the colour of the walls and towels.
I used a paper-piecing pattern for the feature pattern (any could be used such as flowers, boats etc.), and made three pieces.
I made a pattern of the size and shape of the seat (1-1/2 inches larger) and the tank top (1/4 inch larger). Then I worked around them with a mottled black cotton and brought up the other colours used in the main pattern. I made a backing and very light padding piece and put it all together, serging around the edge of the seat cover and putting a 1/2-inch elastic around it, tight enough to hold it firm.
I did binding around the tank top piece.