I wonder if you have heard of SUGRU, I certainly hadn't until recently when I was offered some to play with. The story of its development by Jane whilst she was studying for her MA in Product Design at the Royal College of Art is fascinating and shows a huge commitment to an idea over many years. One of my sons studied Product Design so I was particularly interested. It's actually a serious product with lots of practical applications, but it has also been taken up by the craft community for fun purposes. Here is a link to some of the ways people are using it creatively.
I made some stamps by rolling it out on cling wrap.
I made some flat impressions. My first idea was to use it to take impressions of some stitches. I only did this with a few odd samples etc. and it does leave a slight residue, so don't try it on your precious work. It was a hot day when I tried it and by the time I got to the black piece it was getting stickier. It is like play dough or even blue tack (which I have used before to make prints) but it dries to a firm plastic which allows you to keep the prints/stamps made.
I tried it with a piece of lemon which I once retrieved from the embers of a fire and with a piece of fern. Corks work well to hold the stamps, and in this way you can make three small stamps from one packet.
Wait 24 hours for the Sugru to go firm before printing.
I liked the flat print blocks best and found the way to print them was like lino print i.e. by putting the paper on top of them and then I rubbed the paper with my fingers.