I'm sure it's better when made by a professional, but if you really want to try it, this site has a recipe: https://gluttodigest.com/cube-croissants-square-croissants-with-an-extra-dimension-of-texture/It also mentions some places that sell it, but I'm guessing those are expensive and/or distant.
Buy puff pastry and a cube form.Cut the dough into long triangles and roll into a spiral, fitting the triangle pieces into the box form diagonally.Bake. EZ
There’s gotta be a way to combine cube and croissant but I’m a bit too tired to figure it out. Cubessant? Croib?
GET OUT OF MY HEAD GET OUT OF MY HEAD GET OUT OF MY HEAD
Phew, I'm not the only one that thought it looked sus.