Cut the winch post components as below.
Set the winch post centrally over the winch post base plate and adjust the post (forwards/backwards) so that there will be adequate clearance for getting a spanner in to tighten the U bolt nuts once welded (take into consideration the size of the weld fillet as well).
Fit the Vee plate onto the end of the winch post vee stem and take some time aligning the plate so that it is central and parallel to the top and bottom face of the vee stem. Tack weld into position.
Set the vee stem onto the winch post and again take time to align the stem and post accurately. It doesn't take much of an error to make the winch post look shoddy & poorly built.
Mark the distance from the bottom of the winch post to the top of where the winch plate will be mounted. Check that there is sufficient clearance for fitting your specific winch and adjust the height if required.
Set the tacked winch post on a level surface (clamp or sandbag if required) and centralise and level the winch plate in position and tack weld. Cut and fit a 12mm rod brace and tack weld into position.
Once you are happy with how the winch post looks, fully weld the components together.