We'll leave the time and place up to you, but the focus of your story should be the romantic love between two women, whether it’s a developing affair or an established relationship.
Why not fill in the unwritten chapters of history and show us medieval maidens, Regency belles, Victorians, or wartime women seeking comfort in each other’s arms?
What does the future look like for women who love women? Are they out in space, living on other planets or colonies, human or otherwise? Or still on earth, enslaved or emancipated by new technology, governments, and events?
Or set your story in a world of your own creation, where myths come alive or the supernatural is standard fare. Send your heroines on quests and adventures to prove or discover their love.
Women who love women in fiction rarely get more than an ambivalent ending, so let’s change that. Whatever they have to go through to get there, make sure your characters get their happy ending.