I made this activity to practice the Subject Verb Object Object grammar point, but you can alter it to fit other grammar points if you're practicing another form of explanation.
I start off by showing the class a picture of me and a university professor that I took a lot of classes from. I tell the class that I'm very thankful for her. I write the word "thankful" on the board and ask if anyone knows what it means. You can give a hint by covering the "ful" part because of course students have heard the words "Thank you" before.
I tell the students and then write on the board "I'm thankful to [my teacher], because she taught me Japanese." If I have time, I try to give a couple more examples. "I'm thankful to [another teacher at the school] because he gave me candy." If possible, I try to make sure that the JTE is explaining to the students that this another use of the SVOO grammar pattern. I try and write other words that would work in the sentence (like showed, made, cooked, sang) and then pass out the print to each student.
I ask the students to think of someone (or if they can't think of anyone, something) that they feel thankful for, and then to explain why. This can be a little challenging to write, so having lots of examples on the blackboard helps.
Next, I ask the students to get up and ask 4 classmates what they're thankful for and why. Remember to point out that that the pronoun changes when they're writing the sentence about other people. ("Because he gave her chocolate.")
You can tie this into the Thanksgiving holiday if you want!