It would be easy to design.. Do you have a front row? Have you used the calculators to determine the correct height given front row and distance from screen?
We can design you something easy on this forum. I'm sure others will chime in and coach once you have answered a few questions?. the big key is height and buying wood that meets the height (on its side) to minimize work. Determine how much you want to spend on the wood. For example you can use OSB which is very cheap for the decking.
If the riser is above 9 inches or so you will want a step up. Steps are meant to be a certain height to be standard. If you build a 6 inch step from the ground I guarantee someone will trip. There was a great survey about the subway stairs in NY where one stair was 1/2 in off standard size and there was at least one minor to major injury per day. The ripped the whole thing out.
What is the riser going on top of? Carpet, cement, wood?
Do you want the sides in carpet or wood? Do your want the carpet to roll down over the edges of the deck or to have wood trim such as mine?
Do you know how to lay carpet? do you want glued carpet (easier to lay down, more durable, but tears the deck up if you remove? Or do you want tack stripped carpet?
Glue down can be performed on your own potentially. Tack down usually needs proper stretching and pro.
A patterned carpet is the hardest. Meeting the carpet seems correctly at the roll down on the corner can be near impossible unless you wood trim.
Seams in the carpet is hardest to DIY because you need tools and experience.
Carpet comes in certain widths. To avoid seams, if you glue yourself you will need the smallest width of the stage to be less than this plus the run down the sides.
Buying carpet direct from Georgia and having shipped is the cheapest. Have local shops quote you on just the install.
If you need to take a large roll up or down stairs it is sometimes best to hire this out as well.
Wood decking is very easy but a louder sounding room. I like how the carpet helps to quite the room and feels great when lounging around in socks.