Build the rest of the Nether portal and light it.You have now built the base of your new Nether portal. Replace another block in the floor to your left or right with an obsidian block.Face the same direction you got in step 2 using the F3 screen.Replace the block you are standing on with an obsidian block.

Enter the X Y and Z you got in step 2 into the calculator ('Overworld coords').(We'll use this for getting a smooth transition between the Overworld and the Nether). Remember the direction you're facing when you're walking into the portal as well. Step into the frame and find the coordinates (X Y Z) of the frame on the F3 screen.Build the frame of the portal in the Overworld at your desired location without lighting it.