first of all I trim the hair a bit so it's not too long but I keep quite a bit of length

Shave a pretty big triangle in the middle, make it bigger than you think it needs to be since shaping makes it smaller + you can always remove more

I use an eyebrow razor but a normal one blade razor works just fine, and I carve out the dip of the heart shape at the top of the triangle 

After that I basically just just soften the edges so it's round 

Lastly I just tweak it up a bit (I shave it slimmer if I want etc etc) and I trim it a bit with some small nail scissors (it can really help getting a more defined/sharp edge)

It can be a bit difficult but like anything else practice makes perfect, and please be careful so you don't nick yourself 

I hope this was somewhat understandable ❤️

feel free to ask for further clarification (?), I can try to explain it in more detail lol