[hermitcrab]

To get to the Kármán line (100k) a mountain with a 60 degree slope would require a base of 115km. A cone with 115km diameter base has a volume of 3.5×10^5 km^3. Which is 3.5x10^14 m^3, which is about 10^15 kg of rock. So it is going to take you a while!

[bombcar]

3.5x10⁵ km³ you say?

1.08321×10¹² km³ is the volume of Earth, feasibility study done! Implement!

[hermitcrab]

The molten core probably isn't going to be much use.

Surface area is 5x10^8 km^2. So it it 'only' the first ~2m of the crust (~6m if you don't count ocean).