If you are interested in designing and selling pillows, you might find some useful tips in this blog post.
Choose the medium that you like. It can be drawing, digital art, painting or photographing. If you paint or draw, take a high quality photo of the finished art work. If you do digital art or take photos, you have images ready after finalising the size and the format.
Choose Redbubble, Society6, Fine Art America or some other POD (print on demand) art shop and create an account. It is quite easy to do and all the information needed is on the sites.
Upload your image. Choose all products you like, but here I focus on pillows. Add the image to the pillow section and check that the image fits nicely. You can drag the image so the best part shows up on the pillow. On some shops you can choose rectangular pillows, but most shops have square pillows.
Choose your artist profit, if that is allowed on the site. Usually it is. Scroll down to the end of the page and submit the image. Then have a look at it to see does it look good. If not you can always edit. Edit until you are happy with how the pillow looks.
Now you can buy your own pillows and also share to social media and try to sell your pillows. Easy and fun!