First hot glue the strand of woll to the top rim of the jar to hide the seam area. Do this by just adding a drop of glue, pressing the wool onto it and after about 3 centimeters or about an inch or so, adding the next drop of glue and pressing the wool into it. Keep doing this until the rim is covered. Depending on the size of the rim, this will be about 2-5 rows of wool.
Then fill the jar with decorative rocks in an opposite color. If you used white wool, use green rocks and vice versa.
Last but not least, add the flowers of choice.