1) I'd use
Smashwords for the widest variety of formats, DRM-free and able to sell around the world. Plus great royalties. About as painless as it gets.
2) If you want to sell direct to readers, creat your "store page" on your site and use
Gumroad.com for the hosting and transactions.
Format and upload your files (make it one big zip with all formats inside), you will get a custom Gum.to/ url (shortened, like Bit.ly). Post the url as your "Buy" link and promote the custom url as you would any other. (You can set up your own storepage and mask the gumroad links, too...it's on their blog).
You can have prices from $0+ (give what you want) on up to any set price you choose. Gumroad takes 25 cents + 5% per transaction, so the royalties work out at least as good as Smashwords.
The advantage for you is they handle hosting, commerce, fulfillment...all the challenging stuff. All you have to do is write a great book, format and upload it and let the world know it exists.
The big advantage of Gumroad is for the customer: All they have to do is enter their email address and credit card #, so buying is a piece of cake, making for a very streamlined and easy buying experience.
With both options, you have to promote to make it work...but both Smashwords and Gumroad are open to worldwide customers, great royalties, a variety of formats...all very good things.