Hi xrok1 - use Trim in this case to slice the solid by the curve and divide it into pieces.

I would start by deleting the bottom flat face of the cone underneath if there is one. Then select the cone and run Edit/Trim, select the curve as the cutting object, and then at the next prompt where you can pick pieces to discard, just push Done or right-click to keep all the pieces. Now your cone is divided into 2 pieces by that curve.

Now you can just grab that small piece and slide it out along the y axis, then select the edge around it and the original curve, and do a loft to create the extrusion side-wall part. It is also possible to build this part by using Extrude instead if you want, but you will have to set the extrusion direction.

Then select the 3 surface pieces and use Edit / Join to glue them together. At this point you may want to also delete your projected curve because it will probably get in the way if you want to select edges for filleting after that.

Since you have an open flat base you can cap that off by selecting your shape and use Construct / Planar which will place a trimmed plane along the bottom to seal it into a closed solid.

Let me know if you have any problems following these steps.

- Michael