Using the Combo Blocks plugin, you can set custom width and height for “Featured Image.” This article will help you to set custom width and height for “Featured Image.”
To begin, insert the “Featured Image” block.
Click on the “Featured Image” tab.
Now give your custom “width-length” and select the proper unit of the width-length [ex. 800px].
Then give your custom “Height-length” and select the proper unit of the height-length [ex, 400px].