We have a large Chalkboard wall in our kitchen. We take notes on it, we add seasonal drawings, it's fun and useful. I know we are not the only ones with a chalkboard wall in our house so I thought I would share with you how you can add a customizable clock to your chalkboard wall.

Supplies

A Chalkboard Wall: This almost goes without saying, but I do want to point out that I am using an interior wall of a modern framed and drywalled home. I had no plaster, wires, or insulation to contend with.
Clock Parts: these can be bought at online or at hobby stores. I personally went with a kit that included a battery operated movement, and large, white hands.
Ruler: You will need to be able to measure the dimensions and placement of your clock.
Level: Your clock won't tell time well, if it's not level.
Drywall Knife: You will be cutting a hole in your wall, so be careful.
Small Clock Face: This is used just to cover the movement, not for display.
Black Spray Paint: To help hide the inner workings.
Chalk: To draw your clock face.

Step 1: Measure Twice

First you will need to measure the distance from center of your clock to the tip of the minute hand. The other measurement you need is the size of the movement. Note both of these measurements for the next steps.

Step 2: Position Your Clock

To get the total width of your clock, take the measurement of the hand length from center and multiply by 2. You will need at least this size squared for your clock hands to make their circuit unimpeded. You will probably want to give a little extra room as well. And be sure to keep in mind what may be inside your walls. Wiring, insulation, studs, etc.

Find a good spot on your wall with enough room. I positioned my clock to swing a foot below the ceiling and 3'' from the doorway.

Once you have chosen your spot, mark the center.

Step 3: Measure & Cut Your Hole

Once you cut a hole in your wall, either you put your clock in, or you have to patch it, so let's be sure on this one. : )

From the center you marked, you will need to measure half the size of your movement in each direction. My movement is square, so it was the same distance in all 4 directions, but yours may not be, so plan accordingly. After marking the edges, hold your movement in place against the wall, using your level, and trace all the way around.

You will want the hole to be sized just right. The snugness of the fit is all that holds you clock in place. This will be plenty since clock parts are rather light, but if your cutting is off, you could have trouble. Force your drywall knife into your drywall at each corner of your guide cutting towards the next corner. I made my cuts slightly on the snug side and then shaved it open a bit more, testing the fit as I went.

Step 4: Spray Paint Your Clock Face

To disguise the clock movement, I painted the back of my small clock face black and put it on the the movement backwards. This covers the movement, the edges of the cut drywall, and blends in well with the wall behind.

Step 5: Assemble Clock

Assemble your clock according to the instructions, except for the clock face. Flip this around with the painted side out as a cover. Don't forget to add a battery and set your clock. It's a bit trickier to set you clock with no numbers, but as long as I knew which way was up, I managed without much trouble.

Step 6: Insert Clock Into Wall

This is not permanent, so don't push too far. You will need to replace the battery from time to time. I find it pretty simple to insert the top edge in and then the bottom edge. I only push the movement in to about half depth.