这片面包更薄 英语

This piece of bread is much thinner.

THIS PIECE OF TOAST IS THINNER.应该没错。

This piece of bread is thinner .

如果要突出“更”，用much就可以体现了。
this piece of bread is much thinner.
面包用bread或者toast(所谓的吐司)都可以。

This slice of bread is even thinner.

This slice of bread is thinner.

面包通常都用 slice ，不用的 piece
不用在 thinner 前加 even ，因为 thinner 已经是“更”薄的意思了！呵呵