Can I fix this at home, or do I need to pay for a colour correction?

[CoffeeandCakeEqualsLove]

Pre-lockdowns I had my dark hair bleached every 6-8wks. Over lockdown I got sick of the terrible roots, so I put a ginger box dye on it but it basically went bright orange. So I put a blonde dye on that took the orange off the length, but the roots stayed a bit red. And now my brown roots are coming in...

So basically my hair is 3 colours: blonde, ginger, brown. Is my only at-home option to dye it dark, close to my natural colour?

You'd need bleach to lighten the darker roots or go darker all over

Do you think one of the blonde box dyes with lightener would work all over?

You should get some proper bleach rather than a box dye, and you can probably lift the the orange to blonde, but the brown will probably go orange.

I dyed my orange bits brown so it looked like I had a few inches of dark roots and then light blonde hair. Going to let the whole thing grow out before re-bleaching, I think.

Putting lighter over the already light bits will break it off. It needs correcting. Bleach on the orange, then the roots then tone the lot.

Watch Brad Mondo on YouTube.
Yes you could colour correct it at home with the right product/application.
I'm pretty sure putting that box colour all over will give you blonde roots and shades of orange everywhere else.

Hmm my hair has always held up pretty well to bleaching - having done it at home for a while before going to a salon and it's always been fine with various box blondes...

Maybe I'll wait and ask my hairdresser when I get it cut what she'd charge to clean me up first

Or maybe I need to use ColourB4 to strip the last of the ginger hair dye??

Stay away from the box dye and go to a professional.

Honestly - speak to your hairdresser. Everything you are considering is yet another chemical process, and whilst your hair might have stood up to previous box dyes, it only takes that one last dye to ruin it.