hey y'all , its my first time trying shrink plastic and do u guys know why this is happening 😭😭

here's what ive done so far:

- colored only the rough side

- put it in the oven rough side up

- pressed it down with a heavy book right after taking out

- use foil as liner

- im using a toaster oven that goes up to 250°C, i heat it up for about 5 mins at 250 then bring it down to 200 when putting in the plastics until 8-10 mins