Check your local fire regulations. Fire regulations for your city will determine how far away from the fireplace your surround needs to be. That's a good starting point for how tall and wide it should be.
Cut your 1-by-4, 1-by-6 and 1-by-8 boards to the same length. This length will be the height that you want your fireplace surround. You need these pieces for both sides, so cut a pair of each.
Sand these boards to glassy smoothness. Using a lower grit first, belt sand them until you are using a grit as high as 400. They must be incredibly smooth.
Glue the 1-by-4 onto the 1-by-6, and then, using your screw gun and the 1½-inch screws, screw them together from the back. You don't want any holes showing in the front. Make sure they are flush on one edge, and that will be the outside edge of the frame. You will do this twice--once for each side.
Glue these two boards that are already joined to the 1-by-8 board keeping the edge flush. You should now have a stack that looks almost like a set of stairs. Again, you will do this twice. These "stairs" are the sides of the surround.
Decorate the sides with some grooved lines. Measure out three lines to about 3/4 of the way up each 1-by-4 board. Adjust the fence of your router and rout out the lines precisely in the middle about ½-inch deep. Keep adjusting the fence until all the lines have been cut that deep. Repeat on the other side, routing out the lines. These have been done for decoration and should be well finished and precise.
Mark on the wall how far out your sides need to stand from the fireplace. This will be determined by your own preferences and local fire codes. Most people place them near to the fireplace, but the style of your hearth may require you to place the surround sides farther away.
Attach the surround sides to the wall. Squirt a heavy zig-zag bead of polyurethane adhesive up the masonry wall. Press the boards up against this adhesive. Drill two holes with the masonry bit and hammer drill through the top 6 inches of the 1-by-8 board and into the bricks. Screw in the masonry screws to firmly anchor the boards and repeat on the other side.
Cut the 1-by-10 piece of wood to fit snugly between the uprights. Now that the sides are mounted, measure the distance between them and use this to determine how long the board should be.
Attach the board between the uprights. Using the hammer drill and masonry bit, drill five holes in a line through the upper 2 inches of the 1-by-10, and screw it down with masonry screws.
Decorate the edge of the remaining 1-by-8. Trace a curved pattern into the remaining 1-by-8. This will be your decorative top piece, and realistically, any pattern can be drawn on it that suits your style. Using the jigsaw, cut out the pattern.
Smooth out the top decorative piece. Use your belt sander and 100 grit paper to sand the curves and angles smooth. You may have to do some of this by hand for the ultimate smoothness.
Cut the decorative piece so that it rests snugly over the 1-by-8 side piece, which will cover up the holes that are securing it to the wall. It should be the same length as the 1-by-8 piece when you are done.
Attach the decorative piece. Using your glue, cover the back of your decorative piece where it comes into contact with the back piece. Press it against the back piece.
Mount the mantle piece. Drill ¼-inch holes and countersink them. Add glue where the wood meets, and then screw it on.
Finish your mantle with the stain. You now have a solid fireplace surround. It will need to be finished for the utmost in beauty, so use a high quality stain. The beauty of this surround will dazzle all who see it, and it will last as lifetime.