You can create a single page publication and customize its height.

1. From the My Publications page open the publication you wish and click the Add New Issue button.

2. Go to the Create Blank tab.

3. Specify the number of pages you're going to have. 

Note: Publications can have minimum 4 and maximum 1000 pages. Keep in mind that you may add/remove pages anytime later.

 4. Set the page type as Single Spread.

Warning: This customization does not work with double spread issues.

5. Customize the page width and height. Click Create issua and Finish.

6. When you're done open your issue, go to the page that you wish to customize and click the Edit button.

7. Click the Page Properties tool from the right toolbar and customize the height of the issue.

https://cdn.elev.io/file/uploads/Nx6j1ilgYkjKwwUzxKv9Jx2yWyIGUZG4VbEE9W71H30/-HFu2EHAQV1ErfJgu3xGjw35G8rL1UoNQDK7iHu7N-k/height 00-Vp0.png
Tip: Zoom in the working space and scroll up/down to edit the page content.

That's if, make sure to save your work after editing.