"Jason is making this mock-up" would sound more natural.
Although "Jason makes this mock-up" is technically correct, it does not sound natural. You might be able to use the plural form and add a little more to the sentence, for example, "Jason makes these mock-ups because he thinks he is clever."
Although "does make" is technically correct, the only time I've heard that phrasing is when watching 17th century English drama. "Behold! My lord prince does make the trees to bow!" (Don't ever say that in a modern English setting, please.)
However, its past tense, "did make", is sometimes used in modern English, usually for emphasis. For example:
You would normally say, "Jason made the mock-up".
But if someone questioned your truthfulness, you might say, "Jason DID make the mock-up!"