I make Solomans seals often. These are considered be planetary seals. Generally they should be made in the correct color and on the correct day, hour and under the proper moon phase. And yes, if possible use the correct metal. This is not always possible since lead and mercury are poison and iron is hard and difficult to use.
The readings also say you need to get the blood from the vein of the right wing of bat and a dove feather for a quill or something along those lines. (Used to inscribe the seals with) And we obviously omit doing this one!
I print my seals on paper. Then I make the pentacles of the Sun but just sprinkling some actual gold leaf on and then laminating it. I have also used silver leaf in making the pentacles of the Moon and tin for the pentacles of Jupiter. I had some fine, hair-like copper that I used for my pentacles of Venus.
As for the remaining pentacles, I just make them under all of the other correct corresponding elements and just leave out the metal. But jsyk, there are various herbs that are associated with lead, mercury and iron, etc. You can always infuse some of the herbal “metallic” energy into the talisman, for completeness.
And btw, if all you have is paper and pen then that is all you really need. Use the the elements and put your energy into it. You will, many times, be summoning Angels when making these pentacles and they understand if you don’t have access to all the supplies. Just do your best.
Below is a link to my post on Solomans Seals and a link on how to make them proper.
Goodluck @davethebarbarian