I need idea for simple diy walkway. Needs to be smooth for elderly.

It would help to know what you are starting with. Is this walkway being placed where there is grass now? Or does your walkway need to be above the ground? Level walkway or sloped? Here is a do-it-yourself walkway instruction that may be helpful:

https://www.budget101.com/content.php/502-How-to-build-a-faux-stone-walkway

I would not expect this walkway to stay level and even for long but it will look nice when first installed.

Here are more ideas:

https://www.hunker.com/13424485/cheap-walkway-ideas

The smoothest would be a poured concrete walkway. Next best would be asphalt or interlocking pavers. I am not clear on your budget ir project size. Youtube has instructional videos on each type. Maybe if you review the steps involved you can decide which one is the most doable. You could also solicit bids from local handy persons to compare to diy costs. Hope this helps

Simplest thing I can think of would be a paver walkway. Of course any sidewalk has to start with a level surface, usually dug down 3-4", a layer of landscape fabric and a base of pea gravel, and then sand, set each block in the path and level it with a level and tamp with rubber mallet to make it level. https://www.homedepot.com/p/12-in-x-12-in-x-1-5-in-Pewter-Square-Concrete-Step-Stone-71200/100333077?MERCH=REC-_-PIPHorizontal2_rr-_-302691699-_-100333077-_-N

https://www.youtube.com/watch?v=tsg77seBG2o

https://www.youtube.com/watch?v=QTUuWxBIrU8

This sounds doable! Thanks!