Big, Large
The big radical and the big kanji are exactly the same!
So, if you know the radical, you know the meaning of this kanji as well.
たい, だい
おお
ひろ
There's this big guy (that's how you remember the radical, remember?), and he's wearing a huge Tie Dye (たい, だい) shirt. Because he's so huge, the tie dye shirt is also super huge. Everything about him is pretty big, but the tie dye stands out more than anything.
When you look at the big guy in your head, imagine him covered in tie dye head to toe. Think about how ridiculous it looks on him, especially since he's such a big guy. Shirt. Sweatpants. Hat. Shoes... it goes on and on.