I found good glass and sanded the bottom so it is as flat as it can be. Then I sandwiched peltier module between cpu heatsink and and connected peltier to multimeter to see what I get and also connected it to cheap boost converter from aliexpress that gets 0.9 up to 5V and then put my usb led tester with red led into that.
And it works!
LED lights up and until temperature drops below 60 C led is on.
I have concluded that using combination of thermal pads and paste works better, also putting slight pressure on top of the glass so it sticks harder to the heatsink helps also to get more voltage/current.
In the next log, I will 3d print plastic insulator and try to find some smaller heatsink and try to build better prototype that hopefully can run rgb led.