Use a vertical piece to cover the horizontal piece's square, and use the horizontal piece to cover both vertical pieces' squares.
Then there's only one place the other vertical piece can go.
Wow well i solved it. I dont think i wouldve ever figured that out. Wowowowow. I didnt understand the rules. I must have skipped a section where they teach this or i didnt glean enough info from the previous puzzles.
So what i take away from this is that
it doesnt matter where the blocks go as long as theyre all encapsulated within your outline, youre free to arrange them as you like (without flipping or turning them ofcourse).