Here are just a couple more things that I've made over the past while to help my 3yo with introductory math:
I made this after I saw the unifix stair online. I created the number columns on my computer and glued them to some foam board. I used match sticks to better define the top and bottom of the columns. I followed the Montessori bead stair colors as best I could given the colors that were available from the selection of Unifix cubes I had. The cubes were included in our materials sent by WAVA.
And here's my own version of the Montessori Spindles
This is made from an old curtain I had around the house. I stitched a few simple pockets and used stickyback felt numbers from the craft store.
My 3yo really enjoys both of these activities.
UPDATE: After reading one of the comments from a very kind reader who pointed out the missing "0" from this work, I've since modified the work to look like this: