My recommendation is to use a deck of cards.  Shuffle it to your heart's content, then type in the order of the cards into a string, such as "Ah9d3s3h...".  Hash that and use the resulting 32 bytes as your seed.  You can use armoryengine to do the conversions:  hash256() to hash the string, and "makeSixteenBytesEasy()" to convert each half of the string to a line that can be entered into the wallet restore window.

The order of a deck of cards has 225 bits of entropy, which is plenty big enough.  I tried the dice thing before, but it's a lot of dice rolls and it makes a lot of noise.  The deck of cards is much more pleasant