I sorta figured it out.
https://minecraft.gamepedia.com/Tutorials/Flying_technologies
using the first simple flying machine.
instead of the front red stone block. i put a observer so the out put is on the sticky piston. and connect it with slime blocks to where the slime block is in the front.
this way as i place a block against the observer the machine move forward one. then i can place a block again against the observer.
this allows me to notice if there is server lag because the machine will not move forward.
so i do not have to worry about accidentally building a block and walking on it only to have it disappear with lag.
this shows the back side, which is mostly the normal simple flying machine

this shows the purple pur pur road plus the observer
