The base is a piece of dimensional 2 by 12 planed flat. 45 degree pencil lines from each corner intersect to give points to draw center lines side to side and end to end, without measuring.
These lines help align the tenons on the column with the base.
When you're happy with the placing, draw a line on the base around the end of each tenon. To make sure the column goes with the base the right way round, draw the tip of a triangle on the edge of one oak tenon, with its bottom drawn on the hem/fir base, as in the photo above on the right hand tenon.
The marks round the tenon ends are carried over to the bottom of the base with a square, so the mortices can be chopped through from both sides of the base, meeting more or less in the right place.
Then knock the column through the base. In this case it was such a good fit I didn't need to use glue, but that's not always how these things work out!
The next trick is to add a bit of life, and therefore interest to the joint. Using an offcut of the same oak I cut two right angle triangles, carved a curve into each hypotenuse, and glued them to the front and back of the column at the base. These are sanded so they look like they are part of the original column.
The light coloured part on the left hand side of the top is a shim to get the column level so I can add the top. It's important that the column top is flat to get a good support for the platform for the typewriter.
More to come, bye for now.