I shouldn't be too much of a punk here as Jimmy is right that there are pitfalls with dice. You don't really want to 'roll' the dice as this does bring out the bias...you more want to shake up dice and then slam it down. Doing it in a cup is helpful. With coins you want it to just fall and sit there, no spinning all over the place, or you get that 51% heads outcome.
All still better than 32 bits of entropy but you do start losing a few.
I do think when it comes to this aspect of dice though the perfect becomes the enemy of the good. I'd much sooner take 256 bits that might be 240 that I can examine the generation of before I'll take corrected everything inside a black box that might have an incorrectly written case statement that bypasses it altogether that I won't see. If 240 bits isn't enough it's time for a passphrase and/or multisig.
