Maybe you can make the intangible tangible. A good tool for teaching place values when reading numbers could be an abacus. In those that have 10 beads per line, you can use each line as a place value. When one line reaches 10, have the rule that they must be replaced by 1 bead in the next line. When you teach addition, you can group 2 or 3 lines per place value. Write one number using the first line of each place value group, and then the other number using the second line of each place value group. For every ten beads in a place value group, replace it with 1 bead in the next group. When every group has less than 10 beads, you can write the result.
I especially like those 10x10 abacuses that have 5 beads in one color and 5 beads in another color, switching the order after 5 lines. I got this one for my cousin:
https://www.amazon.com/Learning-Resources-10-Row-Rekenrek-Co...
It helps in visualizing a 1 digit number in more digestible pieces to help working with it in one's head.
Another idea is to use money to emphasize the "worth" of each place value. For example, the first place value could represent pennies, the second dimes, and the third dollars, so each is worth 10 of the place/digit on the right. You can say that it's inconvenient to hold a lot of currency tokens. Why carry 100 pennies or 10 dimes when you can carry a dollar? So, making a number is like reducing the amount of coins or cash notes we carry for the same amount of money.
Yet another idea is to simply show him a giant list of numbers and explaining the patterns in the sequence.