So to start I found just a piece of 2x4 off a pallet that looked relatively decent. I also used a couple different saws/wood glue and a belt sander, the list of all materials are below but you don't need all the saws as you could just get by as long as you have some way to cut wood.

Supplies

1. one 2x4 (as long as needed)

2.Miter saw

3.Bandsaw

4.wood glue

5.Table saw

6.Sandpaper

Step 1: Carving the Inside

First I cut off the ends that were just rot or unusable then I cut it in three pieces on the table saw as seen above.

then I took the center piece, marked out the shape with a pencil and used a bandsaw to cut the needed shape out (I cut it a little smaller so the fit would be better). After that I sanded it to make sure it was straight as you can see in the picture my cutting isn't the straightest.

Step 2: Sanding

For this step I just sanded everything down to my preferred shape and size on the inside to get the blade to fit properly for when it's all glued together so it's pretty simple

Step 3: Gluing and Finishing

Finally you want to glue the three pieces back together once you know everything fits well and make sure to glue it as straight as you can or else it might be unusable. after that you can sand the Seath to a different shape if you want but I wanted a more rustic look and keep the original look to it.