This is the 10975th most frequent Russian word.
вышивкой
Embroidery.
The word 'вышивкой' indicates the instrumental case of 'вышивка' (embroidery) used to describe the method or tool utilized in the action.
Она украсила платье красивой вышивкой.
She adorned the dress with beautiful embroidery.
Here, 'вышивкой' represents the activity of embroidery as a hobby, again in the instrumental case.
Я занимаюсь вышивкой во время досуга.
I engage in embroidery during my leisure time.
'Своей вышивкой' uses 'вышивкой' to denote possession of a defining characteristic, in this case, embroidery, also in the instrumental case.