There's renderings on [1] and [2] and prototype photos on [3] and [4] that makes it look like more of a clamshell / laptop shape with the phone screen and keyboard folded against each other when it's closed. Kind of like a tablet with a keyboard case. Apparently the keyboard will also have a 22Wh/6000mAh batter in it.

[1]: https://www.pine64.org/2020/12/15/december-update-the-longes...

[2]: https://www.pine64.org/2021/01/15/january-update-happy-new-g...

[3]: https://www.pine64.org/2021/02/15/february-update-show-and-t...

[4]: https://www.pine64.org/2021/03/15/march-update/

Search for "keyboard" or just scroll about halfway down each of the pages to see the pictures.