Does anyone know how to enter the nether?

I cant quite get the right combination of blocks to enter the nether world. Would love some feedback

Its a portal made from obsidian, 4 Blocks High, 3 Blocks wide. Hollow in the middle, only the rim should be made.
Then ignite it with a flint and steel and BOOM. Portal to hell itself.

5 obsidian blocks vertical, 4 obsidian blocks horizontal. Then you just light it with flint and steel!



It works with 2 configurations.