I made my pitch lap using Rosin, tempered with little turpentine oil and beeswax. See materials page for more info about these items.
To make the lap, you have to melt the pitch. Use a tin can which is expected to have no future use since you can not use it for any other purpose after melting the pitch in it. I used Haldiram Rasgulla 1 kg tin for this purpose however you can use any other tin can including the old kitchen pan if your mom or wife allows.
I made a full video of pitch lap making. Please check the below video to learn the process. This was made when I was working on my 8 inch mirror. Once you have made your pitch lap, you can proceed to polish your mirror.
Astro Khan Telescope Making 