There is no process defined in the Constitution to split a stateThere is no process defined in the Constitution to split a state
The Constitution of the United States
Article IV
Section 3. New states may be admitted by the Congress into this Union; but no new State shall be formed or erected within the Jurisdiction of any other State; nor any State be formed by the Junction of two or more States; or Parts of States, without the Consent of the Legislatures of the States concerned as well as of the Congress.
Yes, but it does not specifically say how the split is to be determined and the devil is in the details. For example. there are legal scholars (and you know what happens when they get involved) that think that it would take a vote of a majority of the residents of the state in question to allow or tell the legislature how to vote. Then to make it worse some think that the super majority within the area in question should vote for it to make it ok. Others think only “real property†owners should be allowed to vote. Getting an consensus on the plan of how to do it would take years and cause a great deal of BS to be generated by politicians. In the case of West Virginia that was an idea born in Washington to beat an election so it was done in good speed without a lot of BS. Now days I shudder to think how many roadblocks etc would be thrown up.
If it were as simple as the wording you posted would seem to make it then I would be well on the path of getting Northern Nevada to becoming our own state. Part of Kalifornia would come also and it would be called the State of Jefferson.