Assuming there's already been a display of mutual interest through flirting, here are some creative ideas if you don't want to jump right to a candid conversation:
1. Make a collage about your relationship. Some hearts will clue your friend in that this is more than just friendship for you.
2. Make a "story of us" video of your relationship using the best moments. Divide the video into "chapters" like a book, and at the end,
signify "Next chapter?" That's a great segue for having a conversation about where you want this relationship to go.
3. Write a poem if that's your talent. It can be funny or serious.
4. Express your feelings in a letter.
5. Play "Would You Rather" (or 20 Questions) either via texting or in person. Along with silly questions slip in a question or so about would you rather hold hands/kiss/date you or (name an alternative person). This will naturally lead you down a conversation path.
6. Make a playlist of flirty songs. Send them to your crush either as a playlist or text your crush a song every couple of days and tell them why it reminded you of them.
7. If you share an inside joke or interest, buy matching t-shirts or other items.
8. Play a game of "Tell Me Something Awkward." It can be an embarrassing story, something you can never do correctly (like tell right from left), a strange habit, or a crush on a best friend! Since both people take turns admitting awkward things, you never know ... your crush may admit they like you first!