Designing a fireplace mantle requires patience, skills and materials. The first step in designing a fireplace mantle is picking a material, whether it's plywood, brick or another material.
Several home design sites feature articles on building a fireplace mantle. Searching the web or home improvement magazines helps determine what type of mantle to build as well as potential tips. Visit TheIdeaRoom.net and search for "DIY Fireplace Mantel" to find a great article on the before and after of building a mantle.
Building a mantle from scratch requires woodworking tools, a large space and patience. Designing the mantle requires many steps. Expect the project to take several hours, possibly days. The old flat trim must be removed with a putty knife in order to add a new mantle. Then, cut the wood or materials in horizontal and vertical pieces to create the surround. Additional steps will include mitering the wood, adding molding joints and add spackle over any imperfections or visible nails.
Alternatively, search for fireplace mantle kits that come with everything you need to build a stylish mantle. Mantle kits are available from many large retailers, including Home Depot and Lowe's. The kits come in a variety of styles and sizes.