Remove the column on homepage?

Which file would I need to edit in order for me to remove the column blocks completely? I just want to have the promo banner displayed in the middle area of the content section. If I choose not to have anything there, it will display the "empty" box image and I want to remove that area.

Admin>Builders>Page Blocks  Select drop down, "Homepage," you will see your columns below.

Click the big Red "X" to delete them.

That's what I did previously. Which now leaves this "EMPTY" logo. I'm trying to have that removed completely

I'm sure that there's a coding response that is better than this, but you might try to cheat it a bit by creating a blank page block with a blank title as well. Then make the home page with one column only and just that one page block in the column. It will show up as an empty bar and hopefully just like an intentional graphic border.