You can create a single page issue and customize its height.
Note: It is assumed that you are in My Magazines.
Step1. Select the magazine you wish and click the + Add New Issue button.
Step2. Click the Create Blank button.
Step3. Choose the Single Spread option and enter the number of pages you wish to have.
Step4. Click the CREATE ISSUE AND FINISH button.
Step5. Now that you have created your issue it is time to edit it. Click the cover of your issue and then edit it.
Step6. Click the Page Properties tool from the right toolbar and customize the height of the issue.
Note: Zoom in the working space and scroll up/down to edit the page content.
Step7. After editing the page save your work.