To create pull quotes with Gutenberg,
 

1. Click on the Add Block Button
 

2. In the Add Block Panel, click on " Pull Quote", If it doesn't appear, You can also search for it, or click on "Browse all"

 Alternatively, there is also another similar block called "Quotes"
 

3. You will be prompted to type in the quote and its citation

 
Gutenberg also offers out-of-the-box styling options. Simply click on your Quote block to make it active. And on the right panel, click on the "Block" tab: