There are so many great free products on this site that allow teachers to pair students up quickly! You know the type....one student pulls the SNEAKER card. Another pulls the SHOE card. Voila! They are partners! I use a product, free from TPT, in my classroom to do this. It works wonderfully!
However, we don't always want to pair our students up. Sometimes we want them to work in fours, or threes! And sometimes, we have such an odd number that we have some groups of fours and some of threes. If this has ever happened to you, you understand!
So what I did was I created a similar product that features cards to group students into threes or fours. When I look at my class, if I have 23 kids, I might want the group them into 5 groups of 4 and 1 group of 3. That's where my cards come in. I simply take five sets from my "May the Fours Be With You" pile and 1 set from my "Three" grouping set. Voila. Done!
I hope this helps you as much as it helps me. I keep my partner cards, fours, and threes...in a pocket chart for easy access. I am constantly using them to group my students randomly.