remove blue boxes in impress

Linux Mint 18.3 Cinnamon ver 3.67 LO Version:
Build ID: 65905a128db06ba48db947242809d14d3f9a93fe
Selected blank slide without a template have 2 blue rectangular boxes at bottom of every slide. How can I remove these

Actually, there are three boxes. They have the function “date / time”, “footer” and “slide number”. If you don’t need them, you can of course delete them. Go to the sidebar (F11), select “Properties”. There you click on the button “master view”. In the master view you click on the box and click remove. At the top right is the toolbar “Master View” and there you can click on “Close Master View”. Finished.