Doors and Windows - Finishing Touches on Exterior Door

Last fall I installed an pre-hung exterior door. At that time I completed 95% of the job. I would now like to to finish the project. When I finished the door last year I noticed that the front portion of the threshold kind of hung out in mid air. The main frame of the door is supported at the base, just not the front 1/4 to 1/3 of the threshold. Not only that, it isn't trimmed out, just the old siding showing. I would like to some ideas on how to finish. I started to put in 1X4 for bracing the threshold and then finishing it with a piece of siding. But the porch slope a good bit right to left (hinges to deadbolt). It three inches from threshold to porch on right side and five inches on left side. Any other ideas out there. Many ideas are welcome.

Thanks.

why not just use a 1 by board to finish off the bottom too?

to get the slope of your porch on the board buy a board larger than the low side of the slope say it is 4 inches buy a 1*6 and use the transfer method to cut it to conform to the slope so the top will be level to meet the door trim

transfering basically you sit the board down and trace the slope cut this out then cut to a height to fit

hope this helps-----josh