Thank you for all your feedback. It actually made me wondering a bit : why do I need to time myself ?
The only good reason I found is about organisation but in the end it doesn't even matter

I didn't really paint lastly but I played and experienced a bit with what I have for basing.
My first experience was with cork. I was pretty excited and the preparation was going pretty well.

I even cut some base size hole to see how it would look like.


And then came the cutting time ... That was a disaster. Very difficult to cut properly, sand paper doesn't really work and the gap between two pieces is too deep.
As my wife has a some kind of soldering iron for plastic, I tried it on the cork instead of cutting it. I think it worked better but that wasn't enough. Maybe it wasn't hot enough for cork.
I tried to paint it anyway but that looked bad.
Conclusion : I'm sure cork can be useful but not for this. Or at least, it's for me.
Few days later, my coworker came back with the 3D printed object I asked him.

As you can see it's not a roll as I intended to do in the first place. I thought that for the first time I'll go with something easier to use.
With that I could start experimenting with modelling paste. I built some basic shapes that I used for drilling and cutting test. I even let it fall on the ground several times to see if it would break or not. All tests clear ! So far so good. So I went to the next step : using my big stamp.


Used it in 2 different ways : directly on a base and on a wider surface. It's a bit more difficult to put the right amount on a base but the afterwork (is it a real word ?) is easier. And here the wider surface is not thick enough so the pattern isn't clear enough.
In the end, here's how it look like on some bases.

I still have to glue them and drill some holes in it before even starting to paint but I'm really happy with the result so far. And of course I'm also really afraid of ruinning them when I'll start painting.
I'll come back with some news soon enough

Oh and we (French people) are starting lockdown season 2 from this week Friday so I guess I'll have even more time to paint now
