Step 1: Choose a Size

The timer can be a 3 by 2 or a 2 by 3.

Step 2: Add the Redstone Dust

Place two pieces of redstone forming a line. Then, make another line of 2 redstone dust parallel to the other one.

MAKE THE TWO LINES ONE BLOCK APART!

Step 3: Add the Repeaters

Place two repeaters each inbetween the parallel lines, but are facing opposite directions. (Refer to the image if you are having trouble.)

Once placed you have finished your timer.

Step 4: How to Use Your Timer

In order to activate the timer, quickly place and then break a redstone torch. Make sure the torch is not connected to both lines of dust. It should only connect to one.

NOTICE: If both lines of redstone dust are lit, then you were too slow. If you're having trouble then read the text below.

If you find this too difficult because it's so fast then set both repeaters to have a 2 tick delay instead of a 1 tick delay, which is the default delay time. To do this, simply click both repeaters once.