第一:He found (that)it____easy(形容词) to do it.,这样看是不是容易些.
还有个答案,就是什么都不填,
如:I found(find的过去式) it easy to mend door.
I found it difficult to get well with sb.(find it + adj + 不定式inf)
He found that his test failed again.(find + that clause)
find sb do sth 一种状况,反复发生的事情
Find sb doing sth.发现一种动作正在进行
希望有些帮助!