Answer: The amount of work depends on how formal an effect you want. Ideally you would remove the sod, create a compacted base layer and then top that with leveled sand, then add the ornamental paving such as paver bricks, decorative cobbles, or other units. This requires a rigid edging system to stay in place. Most supply yards will provide installation instructions for their products for do it yourselfers.
In a less formal setting where settling is not an issue, you could kill out the grass (or not), lay down some weed barrier matting, top that with several inches of gravel and possibly roll it occasionally to keep the surface a bit firmer. The gravel would need to be topped up from time to time as it will settle due to the foot traffic. Some type of edging is also a good idea to keep the gravel from migrating sideways.
Either method is usually doable although time consuming for the average person who is fairly fit. Gravel and sand and pavers are all very heavy.
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