To create an iron golem you need 4 iron blocks and a jack-o-lantern. Create the jack-o-lantern by using shears on a pumpkin so that it has a face. Iron blocks are created by combining 9 irons, so you will need 36 total iron mined before you are able to create the iron blocks.
This seed (2151361310212770970) will spawn you by 10 or so pumpkins, and iron is plentiful in the hillside nearby.
Create a T shape with the iron blocks, and then add the jack-o-lantern on the top as the head.