Few things in woodworking are as frustrating as trying to make several irregular-shaped pieces exactly the same. The solution is to use a template and a flush trim bit. The bearing on the bit rides against the edge of the template and trims the workpiece to the exact shape of the template.

Template

I use ¼" hardboard to make the template. It's an inexpensive, hard material that doesn't have any voids or knots, and you can shape it easily.

To make a template, start by laying out the shape you want on the hardboard. Or you can cut a full-size pattern out of paper and glue it to the hardboard. Then cut out the shape slightly oversize, and file (or sand) carefully up to the line.

Keep in mind that any notches or gouges on the edge of the template will show up later on the finished pieces, so it's important to take the time to work the edges smooth.

After the template is made, attach it to the workpiece with carpet tape. Then use a band saw (or sabre saw) to cut around the template so the workpiece is about 1/16" larger than the template.

Once the workpiece is cut to rough size, you can rout the last 1/16" of material with a flush trim bit on the router table, see drawing. With the template still taped to the top of the workpiece, raise the router bit up until the bearing rides on the edge of the template, see detail. Then rout in a clockwise direction around the bit.

One thing to keep in mind is the cutting edge of the bit. It should be slightly longer than the thickness of the workpiece. That way, the bit trims the entire thickness of the piece.