Especially true for new authors who need exposure, the best way to grow and curate your readership is by making your book available for free. Once you have scheduled your free book day, submit your book to these websites for maximum visibility. Keep in mind that you should submit your free book to these sites 2 - 4 weeks BEFORE your book is made available for free.
Notify Before Promotion (I suggest one month before)
Here is a handy table to use when you do any sort of book promotion. Use this to help you keep track of what sites you’ve already submitted to, and after your book promotion, which ones worked best.