If you need to cut a large number of linear feet of felt, you may want to look into purchasing a "rotary fabric shear".
The rotary fabric shears use a sharp, semi-round blade, bevelled on one side only, and flat on the back, with flats milled onto the edges making the blade hexagonal or octagonal or whatever. The flat back of the blade runs against a lower anvil that rodes under the material being cut, and some models have a spring loaded honing wheel that runs against the bevelled edge as the blade turns to keep the blade sharp.
The rotary shears are usually manufactured for industrial use for cutting multiple layers of fabric, as well as sheet rubber, carpeting, and other typesu of flexible flooring, and sheet goods.
Bosch used to manufactures a cordless version, model GUS 10.8, that uses their 10.8 volt lithium batteries. The bosch can only cut up to 11mm though. The Bosch isn't officially sold in the USA, but you can usually find them for sale from overseas sellers on ebay.
Otherwise you can find corded rotary shears from a number of manufacturers that work the same. I think most are probably manufactured somewhere or other in Asia, but they likely work well enough. Prices vary, and you would need to check cutting capacity, but a lot of the shears cost $200 or less, and in some cases less than $100.
This model supposedly cuts up to 22mm.
https://www.amazon.com/gp/aw/d/B01A...sr=8-4&pi=AC_SX236_SY340_QL65&keywords=rotary+carpet+shear&dpPl=1&dpID=41JJ-rD%2BvoL&ref=plSrch
This cordless model supposedly cuts up to 1/2", and appears to be identical to the older Swiss made Bosch model that bosch manufactured for a couple decades or more but later discontinued.
https://www.amazon.com/gp/aw/d/B01M...sr=8-1&pi=AC_SX236_SY340_QL65&keywords=rotary+carpet+shear&dpPl=1&dpID=31mbArHQF1L&ref=plSrch
This place has a number of different models to look thru.
http://www.allbrands.com/categories/134
I've only used an older Bosch cordless version that had a practically dead in the grave battery, but the shear sliced thru rubber flooring like it was butter for as long as the battery lasted.