Would it be difficult to recess the tie down loops flush with ground surface? Sticking up things where airplanes taxi are hazardous.
Awesome modeling.
I'm glad you asked that. Gives me a chance to explain, LOL!
Aircraft tie down anchors for bare earth applications that are either hammered into the ground or screwed in - both leaving their eyelets standing just proud of the surface - are still commonly used today.
In fact, most civil aviation authorities, like the FAA and EAA, recommend that light aircraft pilots carry tie down anchors and supplies in the planes. A quick Google search of "aircraft tie down anchors" will return many images of both types (along with other more "proprietary" designs) as well as diagrams of their recommended placement and arrangement. (BTW, tailskid / tailwheel dollies are also still in common use today, and Mr. Google can also offer up a zillion photos of dollies for sale.)
It would seem that WWI aircraft were seldom taxied over any appreciable distances. Engine throttle controls were finicky, and airfield surfaces were rough. Very few (none that I know) of the planes had landing gear brakes, and "steerable" tailskids were only marginally effective. Rudder steer on the ground required a lot of pilot skill with the throttle, and tight turns risked damage to the tailskid if it dug into the ground (not to mention things like digging the wings into the ground or getting a wheel stuck and putting the plane on its nose).
Bottom line, it would seem, is that most ground movement was done by manpower to and from the maintenance areas and the landing areas, so there was very little risk of the pilot actually taxiing over the tie down anchors. The ground crews would certainly know where they had put the anchors to avoid them.
Photos of WWI aircraft actually tied down are pretty hard to find, but there are a few. The main clue that this was regularly done is (in the case of the Camel, here) the tie down loops permanently installed on the bottoms of the lower wings. As for the design of the actual tie down anchors (pins, stakes, etc.), I couldn't find any specific references. However, I tried to imagine what the ground support personnel of a traveling, temporary airfield might use in the situation. Logic seemed to offer two viable suggestions:
First would be some sort of "tent peg" like tie down anchors. The large tent hangers suggest that tent pegs (the large wooden types used by the military) would be common. The ground personnel would certainly be very familiar with erecting and tearing down huge, circus tents. Pounding in more stakes to use as tie down anchors would be an easy job. However, that idea seemed somewhat visually boring and dull.
Another idea was some sort of metal screw-in anchors, perhaps a cut off version of the same screw-in barbed wire posts used at the front line to install barbed and concertina wire barriers. These would also be available in large numbers and offer firm anchor points that could simply be abandoned anytime the airfield was relocated. Screw-in anchors also seem to be the simplest, most secure type in use today. The concept of "screw-in" anchors would not have been unfamiliar to the ground personnel even in WWI.
Finally, I'd note that once one end of the tie-down rope has been fixed to the anchor, it never needs to be untied. It can simply be left tied to the eyelet while the aircraft end would be tied and untied from the plane. When not used, it'd just be laying on ground just like the lanyard ropes for the wheel chocks. This means that the ground crewman doesn't need to constantly fish around in the grass looking for the anchor eyelet. He'd simply pick up the running end of the rope and tie it to the parked aircraft.
So, in my "Bob Ross" little world I decided to model the tie down anchors as if they were made from cut down, screw-in barbed wire posts. I also imagined that after I stumbled over one or two in the grass, as the squadron 1SG, I'd order my troops to paint the "damned things" in some bright color for "safety."
Et voila!