How do I stick Blocks to corners of page?

I'm trying to figure out how i can stick the text blocks at the bottom of my page, whilst also making sure page elements will resize and not overlap?

I've seen flexbox mentioned but I'm unsure how to implement.

https://opossum-tangerine-yhe5.squarespace.com/

pass: hi

Ah Thank you Ziggy! This works on desktop but is there a way to do it also in mobile?

You can remove the first and last lines. i.e. @media.... and the final }