Designing a book cover needs creativity, an understanding of colours and good graphic software skills. However, I suggest you give yourself a chance to try it on your book cover. It is not too difficult with the following platforms and software I mentioned below.
Canva
CorelDraw
Photoshop
Canva
I have seen Canva as one of the good platforms for serving royalty-free cover designs for books. I have used it for my book Necessary words - A Vocabulary Book (you can order it on amazon).
You may pick the royalty-free design for your dream book. Canva also provides the Pro Book Covers. You can edit according to your desire using the platform's editing tool. Canva is not limited to the book covers. It offers compatibility to design interiors for your books, greetings/gift cards, posters, thumbnails for Youtube videos, Channel art, Posters for various social media handles, Background covers and much more.
CorelDraw
CorelDraw is a professional tool for graphic designers. I have seen it used by professionals in the publishing, advertising and printing industry. However, I did not use it yet as I do not have it. If I use it, I will share my experience here.
Photoshop
It is the tool which I have been using since October 2018. Easy to learn and use. It took hardly two weeks to become familiar with it. However, I am not a professional graphic designer. Despite that, I can use it as a Pro to illustrate and design book covers.