Relevant text:
Awaken. Duration: Instantaneous. ...After spending the casting time tracing magical pathways within a precious gemstone, you touch a huge or smaller beast or plant.
It doesn't say anything about a span of time after the agate is carved, or needing to be near the agate at all for the spell to take effect. Taking this to the extreme, could you spend 30 years carving agates, then walk through a forest barefoot with your stored agates across the world. and create an instant horde?
Awaken has a casting time of 8 hours, and consumes an agate worth 1,000 gp as the material component. As per the spellcasting rules (Casting a spell, p. 202 PH:
When a character casts any spell, the same basic rules are followed, regardless of the character’s class or the spell’s effects.
Each spell description in chapter 11 begins with a block of information, including the spell’s name, level, school of magic, casting time, range, components, and duration. The rest of a spell entry describes the spell’s effect.
So anything in the description is the spells effect, and the effect only happens once the spell has successfully been cast. This can cause issues, when the description covers activities that sound as if they should be part of the spellcasting, not the effect, like in this case (burning hands is another good example). Here the text in question is:
After spending the casting time tracing magical pathways within a precious gemstone, you touch a Huge or smaller beast or plant.
This does not say immediately after spending the casting time, so you could think that technically any time after spending the casting time qualifies, even if it is 30 years afterwards.
However the spell has a duration of Instantaneous:
Many spells are instantaneous. The spell harms, heals, creates, or alters a creature or an object in a way that can’t be dispelled, because its magic exists only for an instant.
The entire effect is instantaneous, and it happens as soon as you finish casting the spell. Because of that, you only have an instant to touch the plant or object, not 30 years.
The rules on material components state:
Casting some spells requires particular objects, specified in parentheses in the component entry. A character can use a component pouch or a spellcasting focus in place of the components specified for a spell. But if a cost is indicated for a component, a character must have that specific component before he or she can cast the spell.
If a spell states that a material component is consumed by the spell, the caster must provide this component for each casting of the spell.
A spellcaster must have a hand free to access these components, but it can be the same hand that he or she uses to perform somatic components.
You can't access the components if they are in a secret lair on the other side of the world.
"Provide" is not a game term, so we need to look at the English definition: "1. make available for use; supply" seems like the most fitting one. Placing your stored agates "across the world" is not making them available for use.
You stated that you wanted to "walk through a forest barefoot [...] and create an instant horde". However, you missed the casting time, which is 8 Hours. You must cast the spell each time you want to awaken a plant. This means that each time, you must:
If you find some ability that allows you to cast the spell more quickly, you could use that. However, you still have to provide the spell slots.
A few magic items that could help with this are:
This common magic item from Xanathar's Guide to Everything transforms a shrub planted in it into an awakened shrub over the course of 30 days. It is single-use and is not technically the awaken spell. However, if all you want is awakened shrubs, these are a cheaper way to create said plants.
Alternatively, you could try to collect a bunch of these, as each one grants three castings of Wish. The basic use of Wish is to replicate another spell:
The basic use of this spell is to duplicate any other spell of 8th level or lower. You don’t need to meet any requirements in that spell, including costly components. The spell simply takes effect.
Furthermore, the Ring of Three Wishes doesn't require attunement. However, with that many wishes, you probably have something better to do than create an army of awakened plants. In addition, as a legendary magic item, these are likely to be extremely rare/expensive. At least you don't have to provide the agates!
