Click the pencil icon to open the Page Editor.
Click the block settings cog.
Select Switch Default Layout.
Choose Classic, Headline, or Grid as the Default Layout.
Click Save.
How to switch the default stream block layout between classic, headline, and grid.
Click the pencil icon to open the Page Editor.
Click the block settings cog.
Select Switch Default Layout.
Choose Classic, Headline, or Grid as the Default Layout.
Click Save.