Advice-ground prep after clearance

Hi all, sorry if this is lack of common sense….

Wondering what to do with two areas of my garden. Recently had shrubs and brambles chopped down, with stumps left over.

I want to prepare these areas for new plants, and happy to wait a year+ if that’s what it takes.

If I put down cardboard + compost:

1) Would I need to apply a raised border with bricks of some sort to hold it all in or can I leave it overlapping the patio? 2) should I dig out brambles as they come back or before I lay cardboard? 3) would you dig out the stumps? (I realise this is just about personal taste/end goal) 4) will this amount of thick dead sticks be ok to leave under or should I remove as much as possible? 5) mostly, I want the allium triquetrum to die, die, die. Will happen, yes?