Structuring Monday Hour 1?

I got some new freelance work and I have no idea how long it’s going to take me. I’m estimating 3 to 4 hours per assignment. How can I structure this into my Monday Hour 1 Calendar?

Sometimes articles take me 2 hours to write but since these are longer I estimate they will take closer to 4 hours but I don’t want to waste time.

If I have left over time or they take me longer than planned, what should I do?