Grammar

The phrase “making your writing actually look nice” is a participial phrase that modifies the pronoun “that.” A participial phrase acts like an adjective and modifies a noun or pronoun. 

When writing a participial phrase, only the first verb (the present, past, or passive participle) will be tensed. In this example, the verb “making” is a present participle. Any additional verbs in the participial phrase will not be tensed. That’s why “look” is correct.

Here are some more examples:

“You are a master at encouragement, making your friends feel loved.”

“She spent hours baking for the party, making her cake look like a magazine picture.”

Best,

Amy