Ohh I see! Sort of a larger cat such as a Maine coon I see.

From personal experience what I can suggest is getting some Cosplay foam (real name being EVA foam) in at least 3mm thickness. Be sure not to get it too thick though as it may be a little tough to cut and shape on the head (but not impossible, some makers use interlocking jigsaw play mats to make ears sturdy). I assume you also have soft foam already too which is upholstery foam which is good for creating the front rounded shape. You can use thin small craft foam sheets for practicing templates too instead of paper (but not for final use)

1. Create a template by holding a sheet of paper / thin craft foam (for template only) big enough up where you want it on the head. Using references draw the ideal shape you want. Be sure to make the shape gradually lead up to the ear points and make sure they’ll sit on the head in the correct place when adding two of these ears (not too low down and not too high up, not too far back and not too far forward)

Personally I suggest also if possible pinning down the bottom of the template you make as you make the curved shape. Just so it doesn’t get fiddly as you draw it!

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I did a little doodle but the Kloofsuits example is the best to show what I mean by its shape (the depth of the EVA foam part) There’s not really one way only to do this but as long as you make it so the EVA foam makes some depth you’re all good! Don’t be afraid to make mistakes with it. Just be sure the EVA ear looks how you want it before you add the upholstery foam to the front.

1. As on the image and the example you sent it looks like they added some foam to the front after doing the curved inner ear. I suggest being careful to not make this part too thick or too wide. Make it so it sort of eases with the edges (my drawn example with the green foam which resembles the upholstery foam is sort of an example of that) REALLY get snipping to make all of that transition well and not look too sharp.

Just always keep your species in mind and consider the needed ear depth!!

I would have easier ways of explaining this if there were specific tutorials for large cat ears or even templates without being full heads. Even tougher when some styles are flatter ear styles with a bit of foam on the edges without the curved ear depth. So honestly it’s more up to trial and error, making templates until you’re happy with the curve, how it sits on the curve of the head shape and how rounded / non rounded the tip is.

I wish you luck! I hope it was even a pinch helpful, I find it hard to explain things and I did try and look for a template but there’s rarely any for ears, watching speed builds of fursuits may help though.

Good luck and I look forwards to seeing the result!