Adding post grid from PostX as a block.

Hello,

I'm trying to add a post grid at the bottom of each of my blogposts.

I was hoping to do this using a third-party plugin (Post X) to create the grid as a block and then add it to the relevant section of my blogpost.
But when I hit publish the block shows up but doesn't load properly and the styling is off.

Here's what I want it to look like: https://imgur.com/Gr8jq0h

Here's what it actually looks like when published: https://imgur.com/CctHH3O

In case the image isn't clear, it just shows each post aligned vertically and spread across the entire container.

Is there any way to add this block without messing up the styling?

Thanks