1. When viewing the Slide Editor, Select or Hover your mouse over a Block Component in a Lesson Slide to reveal a Trash Bin icon on the top right corner of the Block Component.
2. Click on it to delete the Block Component. The changes will reflect immediately on the Slide Preview as well.
Here is a video walk-through on how to do it:
TIP: You can delete all Block Components on a Lesson Slide and add new ones as you please.
