This activity can be found in the old 'hi, friends books' as well as some old JET manuals. This is the worksheet I use for it.
I use this activity for 1st year junior high and also elementary school 3rd grade. It fits into Let's Try One lesson Five. This works well as a final goal of this lesson. Start with the large copy (you might want to copy it twice at A3 size) to use as demonstrations. The ALT and the HRT get one minute to decide three questions to ask each other and write the topics in katakana. Then one minute each to ask the questions starting with 'What color do you like?'. They should give two answers for example 'I like blue and green'. As they ask they make a memo. If they run out of time that's fine. They can use the information from the questions they did ask to design the t-shirt. Once they have both asked the questions they get two minutes to design t-shirts for each other. After the two minutes they exchange t-shirts and say thank you.
(Note for junior high classes they probably don't have colored pencils or crayons so you'll probably want to leave the first question blank too.)
Now its the students turn. Each page has three t-shirts. I usually cut them out in advance however you can have the students cut them out. The students start with their neighbour as a partner. Follow the same rules as with the ALT/HRT version. One minute to think, one minute each to ask and then two minutes to draw. After they give their t-shirts have the students on the window side of the class move on chair forward. Then repeat the process with new pairs. I find I usually do this two or three times in a 20 minute period including demonstration.
If you are doing it with Let's Try One then the vocabulary practice I've linked this too can be useful before doing this activity.