diff --git a/phono-server/src/presentation_form.rs b/phono-server/src/presentation_form.rs
index 469d789..f5edce7 100644
--- a/phono-server/src/presentation_form.rs
+++ b/phono-server/src/presentation_form.rs
@@ -8,7 +8,12 @@ use serde::Deserialize;
 use crate::errors::AppError;
 
 /// A subset of an HTTP form that represents a [`Presentation`] in its component
-/// parts. It may be merged into a larger HTTP form using `serde(flatten)`.
+/// parts.
+///
+/// WARNING: Though this was originally designed to be combined with
+/// `#[serde(flatten)]`, Serde's buffering strategy causes `flatten` to break
+/// deserialization of `Vec<_>` fields when provided with a sequence of length
+/// == 1. `#[serde(flatten)]` should be avoided.
 #[derive(Clone, Debug, Deserialize)]
 pub(crate) struct PresentationForm {
     pub(crate) presentation_tag: String,
diff --git a/phono-server/src/routes/relations_single/add_field_handler.rs b/phono-server/src/routes/relations_single/add_field_handler.rs
index 224db1b..3fe97d9 100644
--- a/phono-server/src/routes/relations_single/add_field_handler.rs
+++ b/phono-server/src/routes/relations_single/add_field_handler.rs
@@ -34,13 +34,37 @@ pub(super) struct PathParams {
 }
 
 // FIXME: validate name, prevent leading underscore
-#[derive(Debug, Deserialize)]
+#[derive(Clone, Debug, Deserialize)]
 pub(super) struct FormBody {
     name: String,
+
     table_label: String,
 
-    #[serde(flatten)]
-    presentation_form: PresentationForm,
+    presentation_tag: String,
+
+    #[serde(default)]
+    dropdown_option_colors: Vec<String>,
+
+    #[serde(default)]
+    dropdown_option_values: Vec<String>,
+
+    #[serde(default)]
+    text_input_mode: String,
+
+    #[serde(default)]
+    timestamp_format: String,
+}
+
+impl From<FormBody> for PresentationForm {
+    fn from(value: FormBody) -> Self {
+        Self {
+            presentation_tag: value.presentation_tag,
+            dropdown_option_colors: value.dropdown_option_colors,
+            dropdown_option_values: value.dropdown_option_values,
+            text_input_mode: value.text_input_mode,
+            timestamp_format: value.timestamp_format,
+        }
+    }
 }
 
 /// HTTP POST handler for adding a [`Field`] to a [`Portal`]. If the field name
@@ -84,7 +108,7 @@ pub(super) async fn post(
         .fetch_one()
         .await?;
 
-    let presentation = Presentation::try_from(form.presentation_form)?;
+    let presentation = Presentation::try_from(Into::<PresentationForm>::into(form.clone()))?;
 
     query(&format!(
         "alter table {ident} add column if not exists {col} {typ}",
diff --git a/phono-server/src/routes/relations_single/update_field_handler.rs b/phono-server/src/routes/relations_single/update_field_handler.rs
index 1c836b7..c1b674a 100644
--- a/phono-server/src/routes/relations_single/update_field_handler.rs
+++ b/phono-server/src/routes/relations_single/update_field_handler.rs
@@ -21,13 +21,36 @@ pub(super) struct PathParams {
     workspace_id: Uuid,
 }
 
-#[derive(Debug, Deserialize, Validate)]
+#[derive(Clone, Debug, Deserialize, Validate)]
 pub(super) struct FormBody {
     field_id: Uuid,
     table_label: String,
 
-    #[serde(flatten)]
-    presentation_form: PresentationForm,
+    presentation_tag: String,
+
+    #[serde(default)]
+    dropdown_option_colors: Vec<String>,
+
+    #[serde(default)]
+    dropdown_option_values: Vec<String>,
+
+    #[serde(default)]
+    text_input_mode: String,
+
+    #[serde(default)]
+    timestamp_format: String,
+}
+
+impl From<FormBody> for PresentationForm {
+    fn from(value: FormBody) -> Self {
+        Self {
+            presentation_tag: value.presentation_tag,
+            dropdown_option_colors: value.dropdown_option_colors,
+            dropdown_option_values: value.dropdown_option_values,
+            text_input_mode: value.text_input_mode,
+            timestamp_format: value.timestamp_format,
+        }
+    }
 }
 
 /// HTTP POST handler for updating an existing [`Field`].
@@ -44,11 +67,7 @@ pub(super) async fn post(
         rel_oid,
         workspace_id,
     }): Path<PathParams>,
-    ValidatedForm(FormBody {
-        field_id,
-        table_label,
-        presentation_form,
-    }): ValidatedForm<FormBody>,
+    ValidatedForm(form): ValidatedForm<FormBody>,
 ) -> Result<Response, AppError> {
     // FIXME CSRF
 
@@ -57,18 +76,20 @@ pub(super) async fn post(
 
     // Ensure field exists and belongs to portal.
     Field::belonging_to_portal(portal_id)
-        .with_id(field_id)
+        .with_id(form.field_id)
         .fetch_one(&mut app_db)
         .await?;
 
     Field::update()
-        .id(field_id)
-        .table_label(if table_label.is_empty() {
+        .id(form.field_id)
+        .table_label(if form.table_label.is_empty() {
             None
         } else {
-            Some(table_label)
+            Some(form.table_label.clone())
         })
-        .presentation(Presentation::try_from(presentation_form)?)
+        .presentation(Presentation::try_from(Into::<PresentationForm>::into(
+            form,
+        ))?)
         .build()?
         .execute(&mut app_db)
         .await?;