How do I lock a stolen phone, I already removed it from my apple ID is it still possible to lock it?

The phone is “locked” anytime it requires a passcode.

Using “Lost Mode” only provides additional “recovery aids” … it doesn’t make it “more locked” security-wise.

Assuming that you had a secure passcode (known ONLY to you and not easily guessed) the data will remain secure from even sophisticated criminals.

However [unfortunately] since you’ve removed it from your AppleID, it’s no longer “YOUR” phone from an “Apple perspective” and it can be reset (completely wiping it of all onboard info) and re-used by anyone who possesses it.