This material, a box and a ball, is a staple in a Montessori infant/toddler environment and I eventually thought of just making our own Object Permanence Box (and get other Imbucare boxes instead) because I found just the perfect box for it.
This box from Pottery Barn worked nicely.
I cut up the two flaps on the sides to make the ramp inside.
I also cut up a small hole on the box according to the ball's size.
As ball, we're using an old sphere from my Geometric Solids.
The bottom of this Pottery Barn box opens perfectly to look like the door from which the ball will come out of. If you don't have this particular kind, you can always just cut up an arched door.
You may also wrap your box with craft paper. But I decided to leave ours this way since the blue and white already looks pretty enough.
Cara was so excited when I showed her the work and handed her the ball for the first time!
I was too excited too that I forgot to tape up the sides, as you can see right there!
She's feeling the hole just like I showed her.
She's also examining the ball.
Just put the ball right in...
... and see it roll out.
"One test of the correctness of educational procedure is the happiness of the child." - Maria Montessori
And that, that's a happy baby.