Directions for changing the default template for libreoffice are here.
- Open draw, change the page format to landscape
- Save the blank file as a template,
File/Templates/Save
; give your template a name in the New Template box, and click OK - Set the new template as the default template
File/Templates/Organize
;Double-click on My Templates, click on your new template. Click on the down arrow in the Commands button, and pick Set as Default Template, then click OK.