You can set up default blocks via the default option.
This should give you one 1/1 layout with a text block on page creation:
layout:
type: layout
layouts:
- "1/1"
- "1/2, 1/2"
- "1/4, 1/4, 1/4, 1/4"
- "1/1, 1/3, 2/3"
- "1/1, 2/3, 1/3"
- "1/2, 1/2, 1/3, 1/3, 1/3"
default:
- type: text
content:
text: Blabla