I always introduce each new math skill with manipulatives before moving on to abstract numbers on paper. I used the Head of the Class lesson to introduce the skill. They suggested using straws and rubber bands to bundle up the tens. We didn't have straws though we used crayons. Once he figured out that each bundle represented 10 crayons, I brought out my very own home made foam squares.
I got the foam from the Dollar Tree. I drew out 1cm squares on both sides. I just marked the squares with a pen. I made about 200 squares. So I have 1 hundreds square, 9 tens lines, and 10 ones. I am pretty proud of them. They were easy to make and cost me only a dollar! :-) Similar sets cost a lot more.
We compared the line of tens to the ten crayons and saw they represented the same amount. Then I wrote out a 2 digit number, like 27 on the board. My sons have their own dry erase boards which I promise I will blog about and link up to.. Anyway, I wrote the number out on the board and he copied. Then I showed him how to represent that number with the squares.
After he mastered that, I reversed it. I put out a certain number of squares and he wrote the number.
Today, we wrote out number sentences to represent the number. Like 50+4=54 we also reversed it and figured out 54 = 50 + 4 .
As usual my son grasped the whole concept a lot easier than I ever did in school and I realized I had nothing to worry about to begin with.