This is from when my middle kids were somewhere between grades 2 and 5:
My children have 15 minutes for copywork, and they quit at the end of that fifteen minutes whether the selection is finished or not.
Our schedule for copywork for my year 4 child is:
Monday: selection from her nature study book;
Tuesday:Shakespeare;
Wednesday:Literature (Robinson Crusoe was our most recent choice);
Thursday: Bible;
Friday: poetry.
I make selections for them until somewhere around middle school/jr. high. Then they start choosing their own. However, if they don’t, then I continue to make choices for them.
I chose 15 minutes because my girls could write well at those ages. You want to adjust the timer to suit your child.
They need to be able to write neatly and carefully and word by word or line by line (not letter by letter) until the timer is up. Some people help their students write word by word or from memory by putting the source of copywork on the counter and the student writes at the table, getting up to check. Or they can just lay a piece of paper over the material they are copying to cover it while they write, checking now and then for the next section.
Check his copywork to be sure he copied perfectly and point out things he missed- ‘this list of cargo on the ship should have a comma between each thing in the list, titles are capitalized.”
The work you select should be challenging, but not effortlessly easy, and not so challenging it causes frustration. You want just enough of a challenge to require his attention.